Treatment method for rapidly preparing carbon source from kitchen garbage

Abstract

The invention discloses a treatment method for rapidly preparing a carbon source from kitchen garbage. The treatment method comprises the following steps: pretreating the kitchen garbage to obtain slurry; carrying out fermentation treatment on the slurry by using hydrolytic acidification microorganisms so as to quickly hydrolyze and acidify the slurry; heating the material obtained by fermentation, and then carrying out three-phase separation to obtain grease, high-protein solid residues and centrifugate; centrifugate dephosphorization coupled particulate matter coagulating sedimentation: adjusting the pH value of the centrifugate to 6.5-10.5, and sequentially adding a flocculating agent, a dephosphorization agent and a coagulant; separating flocs to obtain high-protein solid residues and a high-quality carbon source. The method disclosed by the invention has the advantages that kitchen garbage is subjected to high-efficiency and low-cost resourceful treatment and is converted into a denitrification high-quality carbon source with low phosphate and no suspended particulate matters for sewage treatment, and meanwhile, grease capable of being used for refining biodiesel and resourceful products such as solid residues for preparing high-protein feed for breeding insects such as hermetia illucens and the like are generated; and full-quantization high-level utilization of organic matter resources is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon source preparation, and in particular to a technology for preparing carbon source by utilizing kitchen waste. Background Art

[0002] Kitchen waste includes household kitchen waste, restaurant kitchen waste, and other kitchen waste. Kitchen waste mainly comes from the catering service industry, canteens of enterprises and institutions, food processing enterprises, urban sewers and grease traps, and households. Anaerobic digestion is the main technology for centralized treatment of restaurant kitchen waste, but with the reduction of biogas power generation income and the improvement of wastewater discharge standards, the economic feasibility of anaerobic digestion is being tested, and the kitchen waste treatment industry urgently needs new treatment technologies.

[0003] Given the unique properties of kitchen waste, the industry usually adopts similar pretreatment methods: kitchen waste undergoes sorting, crushing, pulping, heating and other process flows, and then undergoes three-phase centrifugation to separate oil and fat after pretreatment, and obtains three-phase centrifugal solids and three-phase centrifugal liquid. Among them, oil has a higher economic value and is usually used to refine biodiesel. Due to its high protein content, the three-phase centrifugal solids can also be better utilized as a resource, such as feed. However, the high-level resource utilization of the three-phase centrifugal liquid has always been a difficult problem in the industry.

[0004] In recent years, the preparation of three-phase centrifuge liquid as a carbon source has become a hot topic in the industry. After short-range hydrolysis and acidification, the three-phase centrifuge liquid can produce a large amount of small molecular organic acids, such as lactic acid, acetic acid, propionic acid, etc., with a chemical oxygen demand (COD) of about 30,000 mg / L. These small molecular organic acids are easily used by denitrifying bacteria in sewage treatment, so they have the potential to be used as carbon sources for sewage treatment. However, the three-phase centrifuge liquid after hydrolysis and acidification contains a large amount of suspended particles (SS≈10,000 mg / L) and phosphates (TP≈500-1000 mg / L). The suspended particles are mainly composed of protein and cellulose, so the total nitrogen content of the three-phase centrifuge liquid is also high (TN≈2000-3000 mg / L). If the three-phase centrifuge liquid after hydrolysis and acidification is directly used as a carbon source for sewage denitrification, a large amount of suspended particles will increase the sludge production and reduce the sludge retention time, which is easy to cause the sewage treatment system to collapse; at the same time, the introduction of organic nitrogen and phosphate will increase the system load and increase the risk of substandard effluent.

[0005] The patent document with the announcement number CN 215667619U discloses an integrated restaurant kitchen wastewater treatment device. The transfer wastewater mentioned therein has similar physical and chemical properties to the three-phase centrifugal liquid of restaurant kitchen waste. The technology uses flocculation and sedimentation to remove particulate matter in the transfer wastewater. Although it can reduce the subsequent biochemical treatment load, it has no effect on removing ammonia nitrogen and phosphate in the transfer wastewater.

[0006] A method for preparing a biocarbon source from high-concentration organic waste liquid is disclosed in a patent application document with publication number CN117285120A. The method uses a ceramic membrane filtration method to remove particulate matter, which is costly, and the ceramic membrane filtration method cannot remove soluble phosphates, resulting in a high phosphate content in the carbon source product.

[0007] The patent application document with publication number CN112645546A discloses a method for preparing an organic carbon source from kitchen wastewater, its device and application. It adopts an advanced oxidation method, which is relatively costly; and the patent adopts a method of precipitation followed by fermentation, so some hydrolyzable and acidified particles are removed in advance, reducing the amount of organic acid produced, so that the final carbon source product has a lower COD equivalent.

[0008] A method for preparing a high-efficiency carbon source is disclosed in a patent application document with publication number CN117534258A. This technology adds phosphate and magnesium salts to high-ammonia nitrogen wastewater to form struvite to remove ammonia nitrogen, but cannot effectively remove other particulate matter and phosphates, and the quality of the obtained carbon source is poor.

[0009] Therefore, if a technology can be developed to use kitchen waste to prepare a carbon source without suspended particles and phosphates, it will provide a high-quality carbon source for sewage treatment. Summary of the invention

[0010] The purpose of the present invention is to provide a method for quickly preparing a carbon source using kitchen waste, so as to solve the problem in the prior art that kitchen waste cannot be used to prepare a carbon source without suspended particles and phosphate.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for rapidly preparing a carbon source from kitchen waste, comprising the following steps:

[0013] (1) pre-treating kitchen waste to obtain slurry;

[0014] (2) fermenting the slurry with hydrolytic acidifying microorganisms to rapidly hydrolyze and acidify the slurry;

[0015] (3) heating the fermented material, and then performing three-phase separation to obtain oil, high-protein solid residue, and centrifuge liquid;

[0016] (4) Centrifugal fluid phosphorus removal coupled with particulate coagulation and sedimentation: adjust the pH value of the centrifugal fluid to 6.5-10.5, and add flocculant, phosphorus removal agent, and coagulant in sequence;

[0017] (5) Floc separation to obtain high-protein solid residue and high-quality carbon source.

[0018] Furthermore, the hydrolyzing and acidifying microorganisms are mainly composed of Saccharomyces cerevisiae, Lactobacillus amylovorus, Lactobacillus amylolyticus, Lactobacillus pontis, and Aeriscardovia aeriphila.

[0019] Furthermore, the composition ratio of Saccharomyces cerevisiae, Lactobacillus amylovorus, Lactobacillus amylolyticus, Lactobacillus pontis, and Aeriscardovia aeriphila in the hydrolyzing and acidifying microorganisms is 1:3:3:2:2.

[0020] Further, by weight ratio, the amount of hydrolysis acidification microorganisms used is a microorganism concentration of 10 7 The ratio of bacterial liquid (cfu / ml) to slurry is 10:100, and this is used as the inoculation amount to inoculate hydrolytic acidifying microorganisms when the reactor is started.

[0021] Furthermore, the particle size of the slurry obtained in step (1) is less than 5 mm.

[0022] Furthermore, in step (2), the fermentation temperature is 20-40° C., the hydraulic retention time is 1-4 days, and the reaction mode is semi-continuous or batch.

[0023] Furthermore, in the step (3), the fermented material is heated to 70-100° C., kept warm for ≥30 min, and then separated into three phases.

[0024] Furthermore, in step (4), a pH regulator is used to adjust the pH value of the centrifuge solution, and the pH regulator is a strongly alkaline calcium salt or a combination of a soluble calcium salt and a strong base;

[0025] The strong alkaline calcium salt includes one or two of calcium hydroxide and calcium oxide;

[0026] The soluble calcium salt in the soluble calcium salt and strong base combination agent includes one or more of calcium chloride, calcium bicarbonate, and calcium dihydrogen phosphate, and the strong base includes one or more of sodium hydroxide, potassium hydroxide, and barium hydroxide.

[0027] Furthermore, the process of step (4) includes: adjusting the pH of the centrifugal liquid, adding an aluminum salt flocculant to the centrifugal liquid, and stirring; then adding a magnesium salt dephosphorizing agent, and stirring; and then adding a coagulant polyacrylamide, and stirring.

[0028] Furthermore, the aluminum salt flocculant is one or more of polyaluminum chloride, polyaluminum ferric chloride, aluminum chloride, and aluminum sulfate;

[0029] The aluminum salt flocculant is added in an amount of 0.0025% to 0.2000% by weight of the centrifuge liquid;

[0030] The magnesium salt dephosphorization agent is one or both of magnesium chloride and magnesium sulfate, and the amount of the magnesium salt dephosphorization agent added is 0.01 to 0.1% by weight of the centrifuge liquid;

[0031] The added amount of the polyacrylamide aqueous solution is 0.0030% to 0.0150% by weight of the centrifugal solution, and the polyacrylamide is prepared into a polyacrylamide aqueous solution with a weight fraction of 2 to 3% when used.

[0032] Furthermore, the aluminum salt flocculant is added in an amount of 0.025% to 0.050% by weight of the centrifuge liquid;

[0033] The magnesium salt dephosphorization agent is added in an amount of 0.05% by weight of the centrifuge liquid;

[0034] The added amount of the polyacrylamide aqueous solution is 0.0040% to 0.0075% by weight of the centrifuge liquid.

[0035] Furthermore, the reaction time of pH adjustment in step (4) is 5 to 30 minutes, and the pH is adjusted to 7.0 to 8.5;

[0036] Add aluminum salt flocculant to the centrifuge liquid, first stir rapidly at 100-300 rpm for 0.5-5 min, then stir at a medium speed of 60-140 rpm for 1-5 min; then add magnesium salt dephosphorizer and stir; then add polyacrylamide and stir at 30-80 rpm for 1-30 min.

[0037] Further, add aluminum salt flocculant to the centrifuge liquid, first stir rapidly at 100-300 rpm for 1 min, then stir at medium speed at 60-120 rpm for 2 min; then add magnesium salt dephosphorizer and stir; then add polyacrylamide and stir at 30-60 rpm for 10 min.

[0038] The key points in the above steps are:

[0039] The pretreatment process is that after the kitchen waste is collected and transported into the factory, it is sorted, crushed, and pulped to separate non-biodegradable substances (such as glass, plastic, wood and bamboo, etc.) and recyclables (such as metal), and is homogenized into a slurry with a particle size of less than 5mm.

[0040] After fermentation, organic matter such as starch in the slurry is converted into small molecule organic acids such as lactic acid and acetic acid, while proteins, oils, etc. in the slurry remain stable.

[0041] Kitchen waste contains a large amount of oil, 5 to 10 wt%. After pretreatment, fermentation, hydrolysis and acidification, the oil is suspended in the slurry in the form of colloid. Heating can effectively destroy the stability of the oil particles, causing them to become unstable and coagulate.

[0042] Due to fermentation, hydrolysis and acidification, the acidic component contained in the three-phase centrifuge liquid is mainly lactic acid, and the pH value is between 3.5 and 3.8, which is slightly acidic. The pH value has a great influence on the subsequent deammoniation and phosphorus removal as well as particulate coagulation, so the pH of the centrifuge liquid needs to be adjusted.

[0043] The nitrogen in kitchen waste mainly comes from protein, and the phosphorus mainly comes from cell membranes and phytic acid. During the collection, transportation, pretreatment, fermentation, rapid hydrolysis and acidification of kitchen waste, the microorganisms in the kitchen waste decompose some phosphorus-containing substances into phosphates. It has been determined that phosphate accounts for about 80% of the total phosphorus in the kitchen waste slurry after rapid hydrolysis and acidification (400-600 mg-P / L).

[0044] Centrifugal liquid phosphorus removal coupled with particle coagulation and sedimentation is to chemically precipitate phosphates and coagulate the chemical precipitation particles and small-size organic particles in the three-phase centrifugal liquid into flocs. This step can be carried out in batch or continuous mode, and can be completed in one reactor or multiple reactors in series. The addition method can be direct addition or pipeline mixer addition.

[0045] The addition of magnesium salt and phosphate ions generates magnesium phosphate precipitate to achieve the purpose of phosphorus removal.

[0046] Polyacrylamide (PAM) is a linear water-soluble polymer with a large number of amide groups on the main chain of the molecule. It can react with a variety of compounds to produce many polyacrylamide derivatives. At the same time, the amide groups can also combine with a variety of substances through hydrogen bonds to promote flocculation. After adding PAM, stir slowly to promote colloid coagulation.

[0047] The floc separation methods include free sedimentation, membrane filtration, flotation, centrifugation, screw extrusion, plate and frame filter press and any other common floc separation and dehydration methods.

[0048] The advantages of the present invention include: utilizing kitchen waste for resource processing efficiently and at low cost; kitchen waste can be converted into a low-phosphate, high-quality denitrification carbon source without suspended particles for sewage treatment within 1.5 to 3 days; and resource products such as oils and fats that can be used to refine biodiesel and solid residues that can be used to prepare high-protein feed for insect breeding such as black soldier flies are produced. The above-mentioned carbon sources, oils and fats, and solid residues can all be sold as raw materials, thereby realizing full-scale and high-level utilization of organic resources.

[0049] Saccharomyces cerevisiae can secrete cellulase, which breaks down cellulose into cellobiose and glucose and produces ethanol. Lactobacillus amylovorus and Lactobacillus amylolyticus can secrete amylase, which quickly converts starch into small-molecule sugars and converts them into lactic acid. Lactobacillus pontis and Aeriscardovia aeriphila can quickly utilize these small-molecule sugars and convert them into lactic acid and acetic acid.

[0050] If the treatment is carried out in the order of heating-three-phase centrifugation-fermentation-phosphorus removal, the phosphorus removal coupling requires the addition of alkali to adjust the pH to neutral, and the fermentation microorganisms will use organic matter to produce hydrogen at a neutral pH, which is dangerous. According to the fermentation-heating-three-phase centrifugation-pH adjustment sequence of the present invention, the heating operation after fermentation is not only conducive to the separation of oil and fat, but also can kill microorganisms, and will not produce hydrogen, which can avoid danger.

[0051] Phosphates in the three-phase centrifugal liquid are chemically precipitated by adding reagents to the neutral centrifugal liquid combined with mechanical stirring; at the same time, small-sized particles in the three-phase centrifugal liquid that have not been centrifugally separated can be flocculated into large-particle flocs, and high-quality carbon sources and solid particles are obtained through the floc separation step; dephosphorization and removal of suspended particles are completed simultaneously in the same coagulation reactor. Since the solid particles in the slurry are mainly composed of protein, the solid particles obtained by three-phase centrifugation and floc separation are a high-protein solid residue.

[0052] After the coagulation and sedimentation, the coarse precipitate is collected at the bottom of the solution, and the upper part is the clear liquid. The water content of the three-phase centrifugal liquid is about 98.5%, the water content of the bottom precipitate is about 90-93%, and the floating particles (SS) of the supernatant are 800-1200 mg / L.

[0053] The carbon source product obtained after floc separation is of high quality, with a suspended particle content of no more than 800 mg / L; an ammonia nitrogen content of no more than 200 mg / L; and a total phosphorus content of no more than 200 mg / L.

[0054] The investment and processing costs are low. The process does not require large reactors or large equipment. The hydrolysis and acidification reaction cycle is short, so the reaction tank volume is small. The entire process covers an area of ​​no more than 5m 2 / (t·d). BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0056] Figure 1 This is a graph showing the precipitation effect of the three-phase centrifuge liquid flocculation reaction at different pH values ​​adjusted by sodium hydroxide and then left to stand for 15 minutes;

[0057] Figure 2 This is a graph showing the precipitation effect of the three-phase centrifuge liquid after flocculation reaction and standing for 15 minutes at different PAC dosage values ​​when the pH value is adjusted with sodium hydroxide;

[0058] Figure 3 This is a graph showing the precipitation effect of the three-phase centrifuge liquid after flocculation reaction and standing for 15 minutes at different PAM dosage values ​​when the pH value is adjusted with sodium hydroxide;

[0059] Figure 4 This is a graph showing the precipitation effect of the flocculation reaction of the three-phase centrifuge liquid at different pH values ​​adjusted by calcium hydroxide and then left to stand for 15 minutes;

[0060] Figure 5 It is the precipitation effect of the three-phase centrifuge liquid after flocculation reaction and standing for 15 minutes at different PAC dosage values ​​when the pH value is adjusted by calcium hydroxide;

[0061] Figure 6 It is the precipitation effect of the three-phase centrifuge liquid after flocculation reaction and standing for 15 minutes at different PAM dosage values ​​when the pH value is adjusted by calcium hydroxide;

[0062] Figure 7 This is a graph showing the precipitation effect of the three-phase centrifuge liquid after the flocculation reaction of calcium hydroxide emulsion at different pH values ​​(7-10) and then standing for 15 minutes;

[0063] Figure 8 is a flow chart of Embodiment 1;

[0064] Fig. 9 is a flow chart of Embodiment 2;

[0065] Fig.10 This is a flow chart of Example 1;

[0066] Fig.11 This is a flow chart of comparative example 2. DETAILED DESCRIPTION

[0067] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0068] Firstly, the effects of different combinations of reagents and different usage methods on floc separation were discussed.

[0069] The raw materials and reagents used in the experiment are as follows:

[0070] 1. Raw materials: three-phase centrifuge liquid obtained by the method of the present invention (slurry fermentation-heating-three-phase centrifugation).

[0071] 2. NaOH solution: 1 mol / L, mass concentration 4%. Weigh 40 g of sodium hydroxide (NaOH) and dissolve it in 1 L of water.

[0072] 3. Calcium hydroxide emulsion: concentration 20%, weigh 20g calcium hydroxide (CaOH2) and dissolve it in 80ml water.

[0073] 4. Flocculant: 2.5% polyaluminium chloride (PAC) solution. Weigh 25g PAC, dissolve it and make up to 1L water.

[0074] 5. Coagulant: 0.3% cationic polyacrylamide (PAM) solution. Weigh 3g PAM and dissolve it in 1L water.

[0075] The following experiments were conducted on the combination and addition amount of each agent:

[0076] 1. NaOH+PAC+PAM combination agent

[0077] 1.1 About the optimal pH value of raw materials

[0078] The pH value of the three-phase centrifugal liquid obtained by the method of the present invention (slurry fermentation-heating-three-phase centrifugation) is 3.7-4.4, which is lower than the optimal pH range of polyaluminium chloride 5.0-7.5. Therefore, it is necessary to adjust the pH value of the stock solution, and at the same time screen out the optimal reaction pH value for the three-phase centrifugal liquid material. In the experiment, the pH values ​​were adjusted to: stock solution pH, 4.5, 5.0, 5.5, 6.0, 7.0, 8.0, 9.0, and the amount of the configured PAC solution added was 2 ml (corresponding to the amount of pure PAC 0.0250%), and the amount of the PAM solution added was 3 ml (corresponding to the amount of pure PAM 0.0045%). The pH of the stock solution was 3.81.

[0079] The test process is as follows:

[0080] (1) Take 200 ml of the three-phase centrifuge liquid and adjust the pH of the raw material with 1 mol / L NaOH solution;

[0081] (2) After the pH was adjusted, PAC solution was added, and the mixture was stirred rapidly at 300 rpm for 1 min and then at 140 rpm for 2 min;

[0082] (3) Add 3 ml of the prepared PAM solution and stir at 80 rpm for 12 min;

[0083] (4) Let stand for 15 minutes, observe the flocculation and precipitation effect, and test the turbidity, COD and pH of the supernatant. The test samples No. 1-8 are the original solution, pH 4.5 sample, pH 5.0 sample, pH 5.5 sample, pH 6.0 sample, pH 7.0 sample, pH 8.0 sample, and pH 9.0 sample. The amount of reagent added at different pH values ​​is shown in Table 1.

[0084] Table 1 Dosage of each agent in pH test

[0085] serial number 1 2 3 4 unit Sample volume 200 200 200 200 ml pH 3.81 4.5 5 5.5 Sodium hydroxide solution dosage 0.00 9.30 13.60 16.00 ml Amount of aluminum chloride solution 2 2 2 2 ml Amount of PAM solution 3 3 3 3 ml serial number 5 6 7 8 unit Sample volume 200 200 200 200 ml pH 6 7 8 9 Sodium hydroxide solution dosage 17.40 19.70 20.60 22.40 ml Amount of aluminum chloride solution 2 2 2 2 ml Amount of PAM solution 3 3 3 3 ml

[0086] The flocculation and sedimentation effect is shown in Figure 1 As shown in the figure, it can be seen that when the pH value of the original solution is adjusted to 5-5.5, the flocculation and sedimentation effect is the best, the alum flowers are large, the sedimentation rate is the fastest, and the optimal pH is 5.5. When the pH value exceeds 6, the alum flowers formed are smaller and the sedimentation rate is the slowest.

[0087] The results of testing the turbidity, COD and pH of the supernatant are shown in Table 2.

[0088] Table 2 Flocculation precipitation supernatant analysis test

[0089]

[0090]

[0091] From the characterization results of the supernatant, the turbidity removal rates at different pH values ​​are comparable, all within the range of 92.5-96.2%. The turbidity removal rate at pH 5.5 is 94.2%. In the same sample, turbidity is linearly related to SS, so the SS removal rate is also about 94%. If the stock solution SS is 12300 mg / L, the remaining SS in the supernatant is about 740 mg / L, which is lower than the effluent index requirement of 1000 mg / L. In the pH range of 3.8-9.0, when the pH is greater than 5, the COD removal rate tends to be stable and no longer increases significantly. At pH = 5, the COD of the supernatant is reduced from 58385 mg / L of the stock solution to 29680 mg / L, and the COD is precipitated by 49.2%. Combined with the flocculation precipitation effect, pH = 5.5 is a better value when adjusting the pH value of the material with sodium hydroxide.

[0092] 1.2 About the optimal dosage of PAC

[0093] The pH of the raw material was adjusted to 5.5 with sodium hydroxide solution, and the amount of PAM solution added was 3 ml. The amount of PAC was optimized, and the proportions of pure PAC were: 0.0050%, 0.0125%, 0.0250%, 0.0375%, 0.0500%, 0.0625%, 0.0750%, 0.1000%, and the amounts of 2.5% PAC solution were: 0.4, 1, 2, 3, 4, 5, 6, 8 ml. The test process is as follows:

[0094] (1) Take 200 ml of the three-phase centrifuge liquid and adjust the raw material pH to 5.5 with 1 mol / L NaOH solution;

[0095] (2) After the pH was adjusted, PAC solution was added, and the mixture was stirred rapidly at 300 rpm for 1 min and then at 140 rpm for 2 min;

[0096] (3) Add 3 ml of the prepared PAM solution and stir at 80 rpm for 12 min;

[0097] (4) Let it stand for 15 minutes, observe the flocculation and precipitation effect, and test the turbidity, COD and pH of the supernatant. The test samples numbered 1-8 are samples to which 0.4, 1, 2, 3, 4, 5, 6, and 8 ml of PAC solution are added, respectively. The amounts of different PAC solutions added are shown in Table 3.

[0098] Table 3 Dosage of each agent in PAC dosage test

[0099]

[0100]

[0101] The flocculation and sedimentation effect is shown in Figure 2 As shown in the figure, it can be seen that PAC has a good flocculation effect on the three-phase centrifuge liquid. When the amount of PAC solution is as low as 0.4ml (corresponding to 0.005% pure PAC), it still shows a certain flocculation and precipitation effect, with obvious stratification, but the flocs are small and do not form a cluster. When the amount of PAC solution is greater than 5ml, the flocs begin to form a cluster.

[0102] The results of the test supernatant turbidity, COD and pH are shown in Table 4.

[0103] Table 4 Analysis of flocculation supernatant in PAC dosage test

[0104]

[0105]

[0106] From the characterization results of the supernatant, the turbidity of the supernatant showed a downward trend with the increase of PAC dosage. After the PAC dosage exceeded 5ml (corresponding to the pure PAC dosage greater than 0.0625%), the downward trend slowed down, from 15768NTU of the original solution to 1253NTU, and the turbidity removal rate was 92.1%. The change trend of the supernatant COD also decreased with the increase of PAC dosage. After the PAC dosage exceeded 5ml (corresponding to the pure PAC dosage greater than 0.0625%) COD, it tended to be stable. At this time, the supernatant COD was 30399mg / L, which was 38.5% lower than the original solution COD 49398mg / L. Combined with the floc size and agglomeration, turbidity and COD, the optimized pure PAC dosage was 0.0625%.

[0107] 1.3 About the optimal amount of PAM

[0108] The raw material was adjusted to pH 5.5 with sodium hydroxide solution, 5 ml of 2.5% PAC solution was used, the amount of PAM was optimized, the proportions of pure PAM were: 0.0015%, 0.0030%, 0.0045%, 0.0060%, 0.0075%, 0.0090%, 0.0120%, 0.0150%, and the amounts of 0.3% PAM solution were: 1, 2, 3, 4, 5, 6, 8, 10 ml. The test process is as follows:

[0109] (1) Take 200 ml of the three-phase centrifuge liquid and adjust the raw material pH to 5.5 with 1 mol / L NaOH solution;

[0110] (2) After the pH was adjusted, 5 ml of PAC solution was added, and the mixture was stirred rapidly at 300 rpm for 1 min and then at 140 rpm for 2 min;

[0111] (3) Add the prepared PAM solution respectively and stir at 80 rpm for 12 min;

[0112] (4) Let stand for 15 minutes, observe the flocculation and precipitation effect, and test the turbidity, COD and pH of the supernatant. The test samples numbered 1-8 are samples with PAM solution dosages of 1, 2, 3, 4, 5, 6, 8, and 10 ml, respectively. The addition amounts of different PAM solutions are shown in Table 5.

[0113] Table 5 Dosage of each agent in PAM dosage test

[0114]

[0115]

[0116] The flocculation and sedimentation effect is shown in Figure 3As shown in the figure, the sedimentation process is observed and it can be seen that when the dosage of PAM solution exceeds 2.0% (corresponding to the dosage of pure PAM 0.0060%), the floc sedimentation rate no longer changes, but the flocs do not form a mass.

[0117] The results of the test supernatant turbidity, COD and pH are shown in Table 6.

[0118] Table 6 Analysis and test of flocculation precipitation supernatant in PAM dosage test

[0119] serial number Original solution 1 2 3 4 unit Turbidity 18675 2528 1635 1678 1340 NTU Turbidity removal rate - 86.5％ 91.2％ 91.0％ 92.8％ COD 62030 36047 34301 32042 33993 mg / L COD removal rate - 41.9％ 44.7％ 48.3％ 45.2％ pH 3.79 5.13 5.07 5.12 5.16 serial number Original solution 5 6 7 8 unit Turbidity 18675 1308 1275 1209 1297 NTU Turbidity removal rate - 93.0％ 93.2％ 93.5％ 93.1％ COD 62030 33788 33377 32042 32453 mg / L COD removal rate - 45.5％ 46.2％ 48.3％ 47.7％ pH 3.79 5.09 5.11 5.02 5.07

[0120] From the characterization results of the supernatant, the turbidity of the supernatant showed a downward trend with the increase of PAM dosage. After the dosage of PAM solution exceeded 2.0%, the downward trend stabilized, and the turbidity removal rate was 92.8%. The change trend of supernatant COD also decreased with the increase of PAM dosage. After the dosage of PAM solution exceeded 1.5%, the downward trend stabilized, and the COD removal rate was 48.3%. Combined with the floc settling rate, turbidity and COD judgment, the optimal dosage is 1.5-2.0% of the PAM solution, corresponding to 0.0045-0.0060% of pure PAM.

[0121] 2.Ca(OH)2+PAC+PAM combination agent

[0122] 2.1 About the optimal pH value of raw materials

[0123] When sodium hydroxide is used to adjust the pH value of the three-phase centrifugal liquid from 3.81 to 5.5, the average usage of pure sodium hydroxide is 0.24%, and the price of sodium hydroxide is about 5,000 yuan / t. When treating the three-phase centrifugal liquid, the cost of sodium hydroxide reagent reaches 12 yuan / t, and accounts for 66% of the reagent cost.

[0124] The price of calcium hydroxide is about 1,000 yuan / t, which is lower than that of sodium hydroxide. It can replace sodium hydroxide, and calcium ions can react with phosphates under alkaline conditions to produce calcium phosphate precipitation to achieve preliminary dephosphorization. Calcium ions have coordination and complexation effects, and can be removed by complexation precipitation with compounds containing hydroxyl, phenolic hydroxyl, and ester bonds in the material. The generated flocs are coarser, easier to agglomerate, and have better precipitation properties, which is more conducive to the separation of flocs at the back end. The amount of PAC solution added is 5 ml, and the amount of PAM solution added is 3 ml, and the pH value is optimized. The pH values ​​in the experiment were adjusted to: stock solution pH, 4.5, 5.0, 5.5, 6.0, 7.0, and 8.0. The test process is as follows:

[0125] (1) taking 200 ml of the three-phase centrifuge liquid, and adjusting the pH value of the raw material with a 20% calcium hydroxide emulsion;

[0126] (2) After the pH was adjusted, 5 ml of PAC solution was added, and the mixture was stirred rapidly at 300 rpm for 1 min and then at 140 rpm for 2 min;

[0127] (3) Add 3 ml of the prepared PAM solution and stir at 80 rpm for 12 min;

[0128] (4) Let stand for 15 minutes, observe the flocculation and precipitation effect, and test the turbidity, COD, TP and pH of the supernatant. The test samples No. 1-7 are the original solution, pH 4.5 sample, pH 5.0 sample, pH 5.5 sample, pH 6.0 sample, pH 7.0 sample, and pH 8.0 sample. The amount of reagent added at different pH values ​​is shown in Table 7.

[0129] Table 7 Dosage of each agent in pH test

[0130]

[0131]

[0132] The flocculation and sedimentation effect is shown in Figure 4 As shown in the figure, it can be seen that calcium hydroxide has a good flocculation and precipitation effect in a wide pH range of 4.5 to 8.0, the flocs are large and easy to form agglomerates. What is more special is that the flocs have better agglomeration properties in an alkaline environment. This is different from the flocculation effect of sodium hydroxide in a smaller range of 5.0 to 5.5, and the flocs when sodium hydroxide is used are not as large as those when calcium hydroxide is used.

[0133] The results of testing the supernatant turbidity, COD, TP and pH are shown in Table 8.

[0134] Table 8 Flocculation precipitation supernatant analysis test

[0135]

[0136]

[0137] From the characterization results of the supernatant, the turbidity removal rates at different pH values ​​were all above 94%. As the pH increased, the turbidity removal rate also increased. When the pH was 8, the turbidity removal rate reached 97.9%. The COD removal rate also increased with the increase of pH. When the pH increased from 4.5 to 8, the COD removal rate increased from 28.7% to 40.3%, and there was no inflection point. The TP removal rate increased from 3.8% to 73.4%, especially when the pH increased from 6 to 7, the TP removal rate jumped from 28.5% to 69.6%. It can be seen that the pH value plays a huge role in the removal of phosphorus by calcium hydroxide.

[0138] Using calcium hydroxide as a pH regulator can generate larger flocs with better agglomeration, especially under alkaline conditions with a pH greater than 7. The TP removal rate is also greatly increased to about 70%. Therefore, when using calcium hydroxide to adjust the pH value, pH = 7 to 8 is a better choice.

[0139] 2.2 About the optimal dosage of PAC

[0140] Use 20% calcium hydroxide emulsion to adjust the raw material pH to 7, add 3ml of PAM solution, optimize the dosage of PAC, the dosage ratios of pure PAC are: 0.0025%, 0.0050%, 0.0125%, 0.0250%, 0.0375%, 0.0500%, 0.0625%, 0.0750%, 0.1000%, and the dosages of 2.5% concentration PAC solution are: 0.2, 0.4, 1, 2, 3, 4, 5, 6, 8ml. The test process is as follows:

[0141] (1) Take 200 ml of the three-phase centrifuge liquid and adjust the raw material pH to 7.0 with 20% calcium hydroxide emulsion;

[0142] (2) After the pH was adjusted, PAC solution was added, and the mixture was stirred rapidly at 300 rpm for 1 min and then at 140 rpm for 2 min;

[0143] (3) Add 3 ml of the prepared PAM solution and stir at 80 rpm for 12 min;

[0144] (4) Let stand for 15 minutes, observe the flocculation and precipitation effect, and test the turbidity, COD and pH of the supernatant. The test samples numbered 1-9 are samples to which 0.2, 0.4, 1, 2, 3, 4, 5, 6, and 8 ml of PAC solution are added. The amounts of different PAC solutions added are shown in Table 9.

[0145] Table 9 Dosage of each agent in PAC dosage test

[0146] serial number 1 2 3 4 5 unit Three-phase centrifuge sample volume 200 200 200 200 200 ml pH 7 7 7 7 7 Calcium hydroxide emulsion dosage 5.4 5.1 5.4 5.3 5.3 ml Aluminum chloride solution dosage 0.2 0.4 1 2 3 ml PAC solution dosage ratio 0.10％ 0.20％ 0.50％ 1.00％ 1.50％ PAM solution dosage 3 3 3 3 3 ml serial number 6 7 8 9 unit Three-phase centrifuge sample volume 200 200 200 200 ml pH 7 7 7 7 Calcium hydroxide emulsion dosage 5.3 5.5 5.6 5.7 ml Aluminum chloride solution dosage 4 5 6 8 ml PAC solution dosage ratio 2.00％ 2.50％ 3.00％ 4.00％ PAM solution dosage 3 3 3 3 ml

[0147] The flocculation and sedimentation effect is shown in Figure 5 As shown in the figure, it can be seen that PAC has a good flocculation effect on the three-phase centrifuge liquid. When the PAC concentration is 2.5% and the dosage is as low as 0.2ml (corresponding to the pure PAC dosage of 0.0025%), it still shows a good flocculation and precipitation effect, and the stratification is obvious and the flocs are large. When the PAC solution dosage is greater than 2ml (corresponding to beaker No. 4, the pure PAC dosage is 0.0250%), the flocs are obviously clumped and the precipitate is granular.

[0148] The results of testing the turbidity, COD and pH of the supernatant are shown in Table 10.

[0149] Table 10 Analysis of flocculation supernatant in PAC dosage test

[0150]

[0151]

[0152] From the characterization results of the supernatant, the turbidity of the supernatant showed a downward trend with the increase of PAC dosage, and the turbidity removal rate was 91.8-94.1%. The change trend of supernatant COD and TP also decreased with the increase of PAC dosage, COD removal rate was 21.2-30.4%, and TP removal rate was 49.9-63.7%. When the PAC dosage was 2ml, the turbidity removal rate was 91.9%, COD removal rate was 30.4%, TP removal rate was 59.8%, and the pH value after reaction was 6.65. The change trend of turbidity, COD, and TP was not obvious. Combined with the floc size and agglomeration, the optimized pure PAC dosage was 0.0250%.

[0153] 2.3 About the optimal PAM dosage

[0154] Use 20% calcium hydroxide emulsion to adjust the raw material pH to 7, the PAC solution is optimized to use 2ml, the pure PAM dosage ratios are: 0.0015%, 0.0030%, 0.00455%, 0.0060%, 0.0075%, 0.0090%, 0.0120%, 0.0150%, and the 0.3% concentration PAM solution dosages are: 1, 2, 3, 4, 5, 6, 8, 10ml. The test process is as follows:

[0155] (1) Take 200 ml of the three-phase centrifuge liquid and adjust the raw material pH to 7.0 with 20% calcium hydroxide emulsion;

[0156] (2) After the pH was adjusted, 2 ml of PAC solution was added, and the mixture was stirred rapidly at 300 rpm for 1 min and then at 140 rpm for 2 min;

[0157] (3) Add the prepared PAM solution and stir at 80 rpm for 12 min;

[0158] (4) Let it stand for 15 minutes, observe the flocculation and precipitation effect, and test the turbidity, COD and pH of the supernatant. The test samples numbered 1-8 are samples with PAM solution dosages of 1, 2, 3, 4, 5, 6, 8, and 10 ml, respectively. The addition amounts of different PAM solutions are shown in Table 11.

[0159] Table 11 Dosage of each agent in PAM dosage test

[0160] serial number 1 2 3 4 unit Three-phase centrifuge sample volume 200 200 200 200 ml pH 7 7 7 7 Calcium hydroxide emulsion dosage 5.6 5.7 5.8 5.7 ml Aluminum chloride solution dosage 2 2 2 2 ml PAM solution dosage ratio 0.0015％ 0.0030％ 0.0045％ 0.0060％ PAM solution dosage 1 2 3 4 ml serial number 5 6 7 8 unit Three-phase centrifuge sample volume 200 200 200 200 ml pH 7 7 7 7 Calcium hydroxide emulsion dosage 5.7 5.7 5.6 5.7 ml Aluminum chloride solution dosage 2 2 2 2 ml PAM solution dosage ratio 0.0075％ 0.0090％ 0.0120％ 0.0150％ PAM solution dosage 5 6 8 10 ml

[0161] The flocculation and sedimentation effect is shown in Figure 6 As shown in the figure, it can be seen that PAM has a good flocculation effect on the three-phase centrifuge liquid. When the amount of PAM solution is as low as 2ml (corresponding to the amount of pure PAM 0.0030%), it still shows a good flocculation and precipitation effect, and the stratification is obvious. When the amount of PAM solution is 4ml (corresponding to the amount of pure PAM 0.0060%), not only the flocculation effect is better, but also the flocs are significantly clustered and granular, which is easy to separate.

[0162] The results of testing the supernatant turbidity, COD and pH are shown in Table 12

[0163] Table 12 Analysis and test of flocculation precipitation supernatant in PAM dosage test

[0164]

[0165]

[0166] From the characterization results of the supernatant, when the dosage of PAM solution is 2 ml, corresponding to the dosage of pure PAM of 0.0030%, the turbidity removal rate is 92.7%, the COD removal rate is 41.2%, and the total phosphorus removal rate is 55.81%. When the dosage of PAM solution is more than 2 ml, the removal effect of turbidity, COD and total phosphorus is also good.

[0167] 3. Centrifugal removal effect

[0168] From the above test, we can know that the flocs are easy to form agglomerates and have good sedimentation properties. The flocs can be quickly precipitated by centrifugal separation to obtain effluent with lower SS. Because the amount of PAC used in the project will be higher than the optimized amount in the small test, the higher the PAC amount, the easier it is for the flocs to form agglomerates, so consider increasing the amount of PAC on the basis of the optimized PAC amount. The pH of the stock solution is 4.3, and the 20% calcium hydroxide emulsion is used to adjust the pH of the raw materials to 7, 7.5, 8, 8.5, 9, 9.5, and 10. The effects of centrifugal treatment and non-centrifugal treatment under different pH conditions are tested. The amount of PAC solution is 5ml (the amount of pure PAC is 0.0625%), and the amount of PAM solution is 5ml (the amount of pure PAM is 0.0075%). The test process is as follows:

[0169] (1) taking 200 ml of the three-phase centrifuge liquid, and adjusting the pH value of the raw material with 20% calcium hydroxide emulsion;

[0170] (2) After the pH was adjusted, 5 ml of PAC solution was added, and the mixture was stirred rapidly at 300 rpm for 1 min and then at 140 rpm for 2 min;

[0171] (3) Add 5 ml of PAM solution and stir at 80 rpm for 12 min;

[0172] (4) Let it stand for 15 min, observe the flocculation and sedimentation effect, and take the supernatant for testing;

[0173] (5) Centrifuge at 3000 rpm for 5 min and take the supernatant for testing. Samples No. 1-7 are pH = 7, 7.5, 8, 8.5, 9, 9.5, and 10, respectively. The amounts of different pH adjusters added are shown in Table 1.

[0174] Table 13 Dosage of medicine

[0175] serial number 1 2 3 4 unit Three-phase centrifuge sample volume 200 200 200 200 ml pH 7 7.5 8 8.5 Calcium hydroxide emulsion dosage 2.15 2.4 2.5 2.6 ml For preparing aluminum chloride solution 5 5 5 5 ml Amount of PAM solution 5 5 5 5 ml serial number 5 6 7 - unit Three-phase centrifuge sample volume 200 200 200 - ml pH 9 9.5 10 - Calcium hydroxide emulsion dosage 2.8 3.1 3.3 - ml For preparing aluminum chloride solution 5 5 5 - ml Amount of PAM solution 5 5 5 - ml

[0176] from Figure 7 It can be seen that the flocs have better agglomeration properties when the pH exceeds 7.5. Observation of the sedimentation process shows that the sedimentation rate is faster when the pH is ≥ 8, and the flocs are more granular. It is more appropriate to adjust the pH to 7.5-8.

[0177] The supernatant test results are shown in Table 14.

[0178] Table 14 Analysis and test of supernatant after flocculation precipitation and centrifugation

[0179]

[0180]

[0181] From the test results in Table 14, for groups 1 to 6, after the flocculation sedimentation was left to stand for 15 minutes, the turbidity, COD, TP, TN and ammonia nitrogen at different pH values ​​were significantly removed, but the differences were not large, which were 96.3-98.2%, 48.9-51.2%, 62.8-74.8%, 28.1-35.8% and 15.98-31.33%, respectively.

[0182] For groups 1 to 7, after centrifugation at 3000rpm, the removal rates of turbidity, COD, and TP were significantly improved. The turbidity after centrifugation was reduced from 400-900NTU obtained by sedimentation and static treatment to about 100NTU; COD was reduced from 65-68g / L obtained by sedimentation and static treatment to 38-43g / L; TP was reduced from 160-250mg / L obtained by sedimentation and static treatment to 90-150mg / L.

[0183] After the pH of the three-phase centrifuge liquid is adjusted and flocculants, dephosphorizers, and coagulants are added in sequence, combined with stirring and centrifugation, the turbidity can be reduced from about 24,000 NTU to about 100 NTU. The turbidity is linearly related to the SS content. The SS of the three-phase centrifuge liquid is about 15,000 mg / L, and the SS is expected to be reduced to 100 mg / L after centrifugation. Therefore, centrifugal separation after flocculation is a feasible means.

[0184] In view of the wider pH application range of calcium hydroxide, larger flocs, easier to agglomerate, cheaper price, and the ability to remove about 80% of total phosphorus, calcium hydroxide was selected as the pH regulator in subsequent tests, and the pH was adjusted to 7.5-8. The three-phase centrifuge liquid with different pH was tested, and it was found that when the initial pH = 3.78, the pure amount of calcium hydroxide adjusted to 8 was 0.63% (mass fraction); when the initial pH = 4.4, the pure amount of calcium hydroxide adjusted to 8 was 0.25% (mass fraction), the average pure amount of calcium hydroxide was 0.44%, the pure amount of PAC was temporarily set at 0.0500%, twice the optimized amount of 0.0250%, and the mass fraction of the pure amount of PAM was slightly higher than the optimized amount of 0.0060%, taking 0.0075%, and the flocs were easier to agglomerate. Centrifugal treatment can quickly and efficiently separate the flocculated precipitate to obtain a supernatant, and the turbidity is greatly reduced, which can be reduced from about 24000NTU to about 100NTU.

[0185] Embodiment 1

[0186] This embodiment provides a method for quickly preparing carbon sources using kitchen waste. Figure 8 As shown, the steps include:

[0187] (1) 100 tons / day of kitchen waste with a fat content of 4.2% (w / w), pre-treated to obtain 90 tons / day of slurry and 10 tons / day of impurities and recyclables;

[0188] (2) fermenting 90 tons / day of slurry produced by pretreatment with hydrolytic acidifying microorganisms to rapidly hydrolyze and acidify the slurry, with an inoculation rate of 10% (w / w) of slurry to inoculate the hydrolytic acidifying microorganism liquid at the start of the reactor, and the fermentation temperature being 35° C.;

[0189] Reaction vessel: 3 complete mixing reactors, each with an effective volume of 120 cubic meters, with heat preservation and stirring, and electric heating.

[0190] Reaction mode: sequential batch, for each reactor: a cycle of 3 days, on the first day, 90 cubic meters of liquid are discharged, and then 90 cubic meters of pre-treated slurry are fed, and the reaction is carried out on the second and third days, and the first day is repeated on the fourth day, and so on. The three reactors are fed in turn;

[0191] (3) heating the fermentation liquid to 70° C. and maintaining it for 30 min, using a centrifugal pump to transport the slurry to a horizontal screw three-phase centrifuge, and then separating the three phases to obtain about 95% of the oil, producing about 4 tons of oil / day, 10 tons of three-phase solid residue / day, and 76 tons of centrifuge / day; using a shell-and-tube heat exchanger to exchange heat between the hot three-phase centrifuge produced and the discharge from the rapid hydrolysis acidification reaction vessel to save energy;

[0192] (4) Use a single coagulation tank equipped with a variable speed mechanical agitator and a decanter. The effective volume of the coagulation tank is 10m 3, 10 tons of material were fed each time for batch reaction. After 10 tons of three-phase centrifugal liquid entered the coagulation tank, the stirring speed of the coagulation tank was 180 rpm, and online pH detection and diaphragm pump feedback adjustment were used. The pH was adjusted to 7.5 by adding 20% ​​(w / w) calcium hydroxide emulsion and reacted for 10 minutes to ensure pH stability;

[0193] Use a diaphragm pump to accurately add 100L of 2.5% (w / w) PAC aqueous solution. After adding the aluminum salt flocculant, first stir quickly (speed 120rpm) for 2min, then stir at a medium speed (speed 80rpm) for 2min, use a diaphragm pump to accurately add 10L of 50% (w / w) magnesium chloride aqueous solution, maintain medium speed stirring (speed 80rpm) for 2min, use a diaphragm pump to accurately add 25L of 2.0% (w / w) PAM aqueous solution, and after adding PAM, stir slowly (speed 30rpm) for 30min. After free sedimentation for 30min, discharge the upper clear liquid through a decanter to precipitate flocs;

[0194] (5) Floc separation: After the above steps, the mechanical agitation of the coagulation tank is turned off, and the upper clear liquid is discharged through a decanter after free sedimentation for 30 minutes. The sludge produced after the bottom floc sediment is dehydrated by the screw stacker is mixed with the three-phase centrifugal solid residue to obtain high-protein fine residue and high-quality carbon source.

[0195] The final products are 61 tons / day of carbon source, 25 tons / day of high-protein fine residue, and 4 tons / day of oil.

[0196] Embodiment 2

[0197] This embodiment provides a method for quickly preparing carbon sources using kitchen waste. Fig. 9 As shown, the steps include:

[0198] (1) 100 tons / day of kitchen waste with a fat content of 5.0% (w / w) is pretreated to obtain 90 tons / day of slurry and 10 tons / day of impurities and recyclables;

[0199] (2) fermenting 90 tons / day of slurry produced by pretreatment with hydrolytic acidifying microorganisms to rapidly hydrolyze and acidify the slurry, with an inoculation rate of 10% (w / w) of slurry to inoculate the hydrolytic acidifying microorganism liquid at the start of the reactor, and the fermentation temperature being 20° C.;

[0200] Reaction vessel: Complete mixing reactor, effective volume 250 cubic meters, with stirring.

[0201] Reaction mode: continuous feeding, the liquid volume in the reactor remains unchanged at 250 cubic meters, and the slurry produced by pretreatment directly enters the reactor; at the same time, the fermentation liquid in the reactor is pumped to the subsequent links.

[0202] (3) The fermentation liquid is heated to 90°C and maintained for 15 minutes. The slurry is transported to a horizontal screw three-phase centrifuge using a centrifugal pump. The centrifuge separates about 95% of the oil and fat, producing about 4.75 tons of oil / day, 10 tons of three-phase centrifugal solid residue / day, and 75.25 tons of three-phase centrifuge liquid / day. A shell-and-tube heat exchanger is used to exchange heat between the hot three-phase centrifuge liquid and the discharge of the rapid hydrolysis acidification reaction vessel to save energy. The three-phase centrifuge liquid is stored in a buffer tank for subsequent steps.

[0203] (4) A three-stage series mixing tank is used, which is lowered in height. The water from the upper mixing tank can flow to the next stage by gravity. Each mixing tank is equipped with a variable speed mechanical agitator. The effective volume of the first, second and third mixing tanks is 2.0m 3 , 0.2m 3 , 0.2m 3 , continuous feeding, feed flow rate maintained at 2.9~3.4m 3 / h, 24h operation, the three-phase centrifuge liquid is pumped from the buffer tank to the first-stage stirring tank, the stirring tank speed is 200rpm, online pH detection and diaphragm pump feedback adjustment are used, and the pH is adjusted to 8.0 by adding 25% (w / w) calcium hydroxide suspension.

[0204] The liquid in the first-stage stirring tank flows to the second-stage stirring tank, and the speed of the second-stage stirring tank is 120rpm. Use a diaphragm pump to accurately add 4.0% (w / w) PAC aqueous solution to the second-stage stirring tank at a rate of 37.5L / h; the liquid in the second-stage stirring tank flows to the third-stage stirring tank, and the speed of the third-stage stirring tank is 60rpm. Use a diaphragm pump to accurately add 50% (w / w) magnesium chloride aqueous solution at 3L / h; the water from the third-stage stirring tank flows to the rear-end buffer tank, and the volume of the buffer tank is 3m 3 The water from the buffer tank is pumped to the rear horizontal centrifuge through a centrifugal pump. A doser and a pipeline mixer are installed behind the centrifugal pump. A diaphragm pump is used to accurately add 3.0% (w / w) PAM aqueous solution at 7L / h. The pipeline transportation process takes about 1.5min, and the flocculation process is completed in the pipeline.

[0205] (5) Floc separation: the flocculated material in the pipeline enters the horizontal centrifuge, where it is centrifuged to obtain high-quality carbon source and flocs after dehydration and compression. The flocs are mixed with the three-phase centrifugal solid residue to obtain high-protein fine residue.

[0206] The final products are 58 tons / day of carbon source, 27.25 tons / day of high-protein fine residue, and 4.75 tons / day of oil and fat.

[0207] Embodiment 3

[0208] The experiment of this embodiment refers to the fermentation method of Example 1, and the kitchen waste slurry is fermented. The difference from Example 1 is that water is used instead of bacterial liquid in this embodiment, and the hydrolysis and acidification effects of adding and not adding bacteria (replacing with water) are compared. The same substrate (kitchen waste) is used in a fully mixed reactor at 35° C. for a reaction time of 2 days. The properties of the fermentation liquids of Example 1 and Example 2 are shown in Table 15 below:

[0209] Table 15

[0210] Lactic acid concentrate Acetic acid concentration Ethanol concentration Hydrolysis rate Acidification rate Add bacteria About 15000mg / L About 4000mg / L About 2000mg / L 55％ 38％ No bacteria added About 12000mg / L About 1500mg / L About 500mg / L 45％ 25％

[0211] It can be seen that adding bacteria is beneficial to obtaining more small molecule organic acids and improving the quality of carbon sources.

[0212] Comparative Example 1

[0213] This comparative example provides a method for preparing a carbon source, such as Fig.10 As shown, the steps include:

[0214] (1) 100 tons / day of kitchen waste with a fat content of 4.2% (w / w), pre-treated to obtain 90 tons / day of slurry and 10 tons / day of impurities and recyclables;

[0215] (2) Heating and centrifugation: heat the slurry to 70°C and keep it for 30 minutes, and use a centrifugal pump to transport the slurry to a horizontal screw three-phase centrifuge. The centrifuge separates about 95% of the oil and fat, producing about 4 tons of oil / day, 10 tons / day of three-phase centrifugal solids, and 76 tons / day of three-phase centrifuge liquid. Use a shell and tube heat exchanger to exchange heat between the hot three-phase centrifuge liquid and the discharge from the rapid hydrolysis acidification tank to save energy;

[0216] (3) fermenting 90 tons / day of three-phase centrifuge liquid produced by three-phase centrifugation with hydrolytic acidifying microorganisms to rapidly hydrolyze and acidify the three-phase centrifuge liquid; the inoculation amount of the liquid:slurry is 10% (w / w), and the hydrolytic acidifying microbial liquid is inoculated at the start of the reactor, and the fermentation temperature is 35° C.;

[0217] Reaction vessel: 2 complete mixing reactors, effective volume 150 cubic meters, with heat preservation and stirring, electric heating.

[0218] Reaction mode: sequential batch, for each reactor: 2 days as a cycle, on the first day, 90 cubic meters of liquid are discharged, and then 90 cubic meters of pre-treated slurry are fed, and the reaction is carried out on the second day, and the first day is repeated on the third day, and so on. The three reactors are fed in turn.

[0219] (4) A single coagulation tank was used, equipped with a variable speed mechanical agitator and a decanter. The effective volume of the coagulation tank was 10m3, and 10t of material was fed each time for batch reaction. After 10t of three-phase centrifugal liquid entered the coagulation tank, the stirring speed of the coagulation tank was 180rpm. Online pH detection and diaphragm pump feedback adjustment were used. The pH was adjusted to 7.5 by adding 20% ​​(w / w) sodium hydroxide and then reacted for 10min to ensure pH stability; 25L of 2.0% (w / w) PAM aqueous solution was accurately added using a diaphragm pump, and after adding PAM, slow stirring was performed at 20rpm for 30min. After free sedimentation for 30min, the upper clear liquid was discharged through a decanter to precipitate flocs.

[0220] (5) Floc separation: After the above steps, the mechanical agitation of the coagulation tank is turned off, and the upper clear liquid is discharged through a decanter after free sedimentation for 30 minutes. The sludge produced after the bottom floc sediment is dehydrated by the spiral stacker is mixed with the three-phase centrifugal solid residue to obtain high-protein fine residue for black soldier fly breeding.

[0221] The final products are 61 tons / day of carbon source, 25 tons / day of high-protein fine residue, and 4 tons / day of oil.

[0222] The disadvantages of Comparative Example 1 are:

[0223] (1) The pretreated slurry contains some easily hydrolyzed and acidified substances, such as starch, which are separated in the three-phase centrifugation, resulting in a reduction in the amount of substrate for subsequent rapid hydrolysis and acidification, resulting in a lower content of small molecule organic acids in the final solution;

[0224] (2) First three-phase centrifugation and then hydrolysis and acidification, so that the liquid entering the phosphorus removal coupled particulate coagulation contains a large number of acidifying microorganisms. After the pH is adjusted to neutral, the hydrogen-producing and acetogenic bacteria in it become active and produce a large amount of hydrogen, which on the one hand causes some flocs to float up, and on the other hand increases the safety risk;

[0225] (3) Only conventional coagulation and sedimentation were performed to remove particulate matter but not phosphate.

[0226] Comparative Example 2

[0227] This comparative example adopts the popular ceramic membrane filtration method in the industry to prepare the carbon source, using the process such as Fig.11 As shown, the process is as follows:

[0228] (1) 100 tons / day of food waste with a fat content of 4.2% (w / w) is pretreated to obtain 90 tons / day of slurry and 10 tons / day of impurities and recyclables;

[0229] (2) The pre-treated slurry is heated to 70°C and maintained for 30 minutes, and the slurry is transported to a horizontal screw three-phase centrifuge using a centrifugal pump. The centrifuge separates about 95% of the oil and fat, produces about 4 tons of oil / day, 10 tons of three-phase centrifugal solids / day, and 76 tons of three-phase centrifugal liquid / day; a shell-and-tube heat exchanger is used to exchange heat between the hot three-phase centrifugal liquid produced and the discharge from the rapid hydrolysis acidification reaction vessel to save energy;

[0230] (3) fermenting 90 tons / day of three-phase centrifuge liquid produced by three-phase centrifugation with hydrolytic acidifying microorganisms to rapidly hydrolyze and acidify the three-phase centrifuge liquid: the slurry is inoculated at a rate of 10% (w / w), and the hydrolytic acidifying microbial liquid is inoculated at the start-up of the reactor, and the fermentation temperature is 35° C.;

[0231] Reaction vessel: 3 complete mixing reactors, effective volume 120 cubic meters, with heat preservation and stirring, electric heating.

[0232] Reaction mode: sequential batch, 3 days as a cycle, on the first day, 90 cubic meters of liquid are discharged, and then 90 cubic meters of pre-treated slurry are fed, and the reaction is carried out on the second and third days, and the first day is repeated on the fourth day, and so on, and the three reactors are fed in turn;

[0233] (4) Use ceramic flat membrane and submerged membrane pool to filter the acidified liquid, and use aeration and regular backwashing to control membrane pollution. The water flow rate of the ceramic membrane is 2.5m 3 / h, the concentrated solution is returned to the rapid hydrolysis acidification mixing reactor.

[0234] (5) The clear liquid after filtration through the ceramic flat membrane still contains a large amount of phosphate. First, sodium hydroxide is used to adjust the pH to 8.0, and then a magnesium chloride solution is added to allow the phosphate and magnesium ions to react to form a magnesium phosphate precipitate. Finally, the magnesium phosphate is removed by precipitation to obtain a carbon source after phosphorus removal.

[0235] Comparing the above embodiments and comparative examples, the quality comparison of the equipment, operation input and final carbon source product is shown in Table 16:

[0236] Table 16

[0237] Security Equipment investment Running costs COD SS TP Active ingredients Embodiment 1 high Low Low ＞40000 ＜800 ＜200 Lactic acid, acetic acid Embodiment 2 high Low Low ＞40000 ＜800 ＜200 Lactic acid, acetic acid Embodiment 3 high Low Low ＜35000 ＜800 ＜200 Lactic acid, acetic acid Comparative Example 1 Low Low Low ＜30000 ＜800 ＞500 Lactic acid, acetic acid Comparative Example 2 high high high ＞40000 ＜50 ＜200 Lactic acid, acetic acid

[0238] It can be seen from the above table that the carbon sources prepared in Examples 1 and 2 have better quality.

[0239] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for rapidly preparing a carbon source from kitchen waste, characterized in that: The steps include: (1) pre-treating kitchen waste to obtain slurry; (2) fermenting the slurry with hydrolytic acidifying microorganisms to rapidly hydrolyze and acidify the slurry; (3) heating the fermented material, and then performing three-phase separation to obtain oil, high-protein solid residue, and centrifuge liquid; (4) Centrifugal fluid phosphorus removal coupled with particle coagulation and sedimentation: adjust the pH value of the centrifugal fluid to 6.5-10.5, and add flocculant, phosphorus removal agent, and coagulant in sequence; (5) Floc separation to obtain high-protein solid residue and high-quality carbon source.

2. The method for rapidly preparing carbon sources from kitchen waste according to claim 1, characterized in that: The hydrolysis and acidification microorganisms are mainly composed of Saccharomyces cerevisiae, Lactobacillus amylovorus, Lactobacillus amylolyticus, Lactobacillus pontis and Aeriscardovia aeriphila.

3. The method for rapidly preparing carbon sources from kitchen waste according to claim 2, characterized in that: The composition ratio of Saccharomyces cerevisiae, Lactobacillus amylovorus, Lactobacillus amylolyticus, Lactobacillus pontis and Aeriscardovia aeriphila in the hydrolysis and acidification microorganisms is 1:3:3:2:

2.

4. A method for rapidly preparing carbon sources from kitchen waste according to claim 2 or 3, characterized in that: The amount of hydrolysis acidification microorganism used is calculated by weight ratio. 7 cfu / ml bacterial liquid:slurry=10:

100.

5. The method for rapidly preparing carbon source from kitchen waste according to claim 1, characterized in that: The particle size of the slurry obtained in step (1) is less than 5 mm.

6. The method for rapidly preparing carbon sources from kitchen waste according to claim 1, characterized in that: In step (2), the fermentation temperature is 20-40° C., the hydraulic retention time is 1-4 days, and the reaction mode is semi-continuous or batch; In the step (3), the fermented material is heated to 70-100° C., kept warm for ≥30 min, and then separated into three phases.

7. The method for rapidly preparing carbon sources from kitchen waste according to claim 1, characterized in that: In the step (4), a pH regulator is used to adjust the pH value of the centrifuge solution, wherein the pH regulator is a strongly alkaline calcium salt or a combination of a soluble calcium salt and a strong base; The strong alkaline calcium salt includes one or two of calcium hydroxide and calcium oxide; The soluble calcium salt in the soluble calcium salt and strong base combination agent includes one or more of calcium chloride, calcium bicarbonate, and calcium dihydrogen phosphate, and the strong base includes one or more of sodium hydroxide, potassium hydroxide, and barium hydroxide.

8. The method for rapidly preparing carbon sources from kitchen waste according to claim 1, characterized in that: The process of step (4) comprises: adjusting the pH of the centrifugal liquid, adding an aluminum salt flocculant to the centrifugal liquid, and stirring; then adding a magnesium salt dephosphorizing agent, and stirring; and then adding a coagulant, and stirring.

9. The method for rapidly preparing carbon sources from kitchen waste according to claim 8, characterized in that: The aluminum salt flocculant is one or more of polyaluminum chloride, polyaluminum ferric chloride, aluminum chloride, and aluminum sulfate; The aluminum salt flocculant is added in an amount of 0.0025% to 0.2000% by weight of the centrifuge liquid; The magnesium salt dephosphorization agent is one or both of magnesium chloride and magnesium sulfate, and the amount of the magnesium salt dephosphorization agent added is 0.01 to 0.1% by weight of the centrifuge liquid; The amount of polyacrylamide added is 0.0030% to 0.0150% by weight of the centrifuge liquid. When used, the polyacrylamide is prepared into a polyacrylamide aqueous solution with a weight fraction of 2 to 3%.

10. The method for rapidly preparing carbon sources from kitchen waste according to claim 8, characterized in that: The reaction time of pH adjustment in step (4) is 5 to 30 minutes, and the pH is adjusted to 7.0 to 8.5; Add aluminum salt flocculant to the centrifuge liquid, first stir rapidly at 100-300 rpm for 0.5-5 min, then stir at a medium speed of 60-140 rpm for 1-5 min; then add magnesium salt dephosphorizer and stir; then add polyacrylamide and stir at 30-80 rpm for 1-30 min.

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