A harmless treatment method for kitchen waste based on thermal hydrolysis

Abstract

The invention discloses a harmless treatment method for food waste based on thermal hydrolysis, which utilizes VOC gas generated by food waste to burn and provide heat for the food waste, thereby achieving standard emission of VOC gas and utilization of VOC gas energy; utilizing alkali washing waste liquid of VOC gas generated by food waste to prepare fertilizer, thereby achieving standard emission of VOC gas and harmless treatment of alkali washing waste liquid, and providing required Na and K elements for fertilizer; utilizing thermal hydrolysis reaction to treat food waste and utilizing reaction products and waste liquid generated in the treatment process to prepare fertilizer, thereby achieving sterilization and inactivation of food waste and harmlessness of reaction products and waste liquid, and can be widely used in the technical field of food waste.

Description

Technical Field

[0001] The invention belongs to the technical field of food waste treatment, and in particular relates to a food waste harmless treatment method based on thermal hydrolysis. Background Art

[0002] Kitchen waste refers to food processing scraps and edible residues generated by households, schools, canteens and catering industries. Its composition is complex, and it is a mixture of oil, water, fruit peels, vegetables, rice, fish, meat, bones, waste tableware, plastic, paper towels and other substances. Kitchen waste has a high water content, poor dehydration performance, is easy to rot at high temperatures, and is easy to breed mosquitoes, flies and bacteria. The treatment of the above kitchen waste has attracted increasing attention.

[0003] At present, the main methods for treating and disposing of restaurant kitchen waste include high temperature disinfection to make fertilizer (feed), aerobic composting, anaerobic fermentation, mixing with domestic waste into landfill system, etc. The current technical difficulty is how to solve the secondary pollution problem after the treatment of restaurant kitchen waste, detailed description:

[0004] High-temperature disinfection technology for making fertilizer (feed): Currently, high-temperature disinfection of kitchen waste is mainly carried out at 100℃~120℃. However, kitchen waste may contain substances such as foot-and-mouth disease, salmonella, toxoplasma, and swine fever bacteria. Some viruses are transformed into spores at this treatment temperature and cannot be completely inactivated. Incompletely treated kitchen waste materials will re-enter the food chain as fertilizer or feed, which may eventually cause human infection with viruses such as foot-and-mouth disease and hepatitis, and may become an "invisible bomb" for the outbreak of infectious diseases at any time.

[0005] Landfill method: Similar to high-temperature sterilization, food waste that has not been thoroughly disinfected may cause an outbreak of infectious diseases.

[0006] Aerobic composting and anaerobic fermentation: Aerobic composting generally takes 10 to 30 days, while anaerobic fermentation takes several months to complete the reaction. During this period, a large amount of odor is continuously generated. For economic reasons, enhanced odor treatment equipment is generally not installed, resulting in odor leakage and environmental pollution. In addition, the organic matter concentration in the residual liquid after composting is extremely high, which cannot be treated by conventional wastewater biological treatment methods, causing secondary pollution.

[0007] In summary, one of the current technical difficulties in the treatment of food waste is how to achieve harmless treatment of food waste without generating solid, liquid and gaseous wastes, or how to achieve harmless treatment of solid, liquid and gaseous wastes during the treatment process, and how to prevent pathogens in food waste from returning to the dining table and causing disease transmission. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for harmless treatment of kitchen waste based on thermal hydrolysis in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem of secondary pollution caused by kitchen waste treatment.

[0009] The present invention adopts the following technical solutions:

[0010] A method for harmless treatment of kitchen waste based on thermal hydrolysis comprises the following steps:

[0011] S1. Sorting and crushing the kitchen waste and collecting the generated VOC gas;

[0012] S2, burning the VOC gas obtained in step S1, and using the heat generated by the combustion to preheat the kitchen waste crushed in step S1;

[0013] S3, performing thermal hydrolysis on the kitchen waste after the preheating treatment in step S2 to obtain an oil phase product, a harmless water phase and solid phase product, and VOC gas;

[0014] S4. Alkali washing is performed on the VOC gas obtained in step S1 and step S3 to obtain alkaline washing waste liquid, and the alkaline washing waste liquid and the harmless water phase and solid phase product obtained in step S3 are used to prepare fertilizer, thereby realizing harmless treatment of food waste based on thermal hydrolysis.

[0015] Specifically, in step S1, the particle size of the crushed kitchen waste is 0.1-1 mm.

[0016] Specifically, in step S1, the sorted plastic products and metal products are cleaned to recover the plastics and metals.

[0017] Furthermore, the obtained cleaning waste liquid is mixed with untreated food waste.

[0018] Specifically, in step S2, oxygen-enriched combustion or staged combustion technology is used to cleanly burn the VOC gas.

[0019] Specifically, in step S3, the temperature of the thermal hydrolysis reaction is 160-350° C., and the pressure is 0.5-20 MPa.

[0020] Furthermore, the oil separated after the thermal hydrolysis reaction at 160-200° C. is used to prepare industrial oleic acid, stearic acid or biodiesel.

[0021] Furthermore, the bio-oil separated after the 280°C high temperature thermal hydrolysis reaction is used to produce fuel oil or chemical raw materials.

[0022] Specifically, in step S4, alkaline washing is performed using a KOH solution or a NaOH solution.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] A method for harmless treatment of food waste based on thermal hydrolysis, wherein the food waste is collected and sorted and crushed, the sorted plastic products and metal products can be recycled after cleaning, and the waste liquid after cleaning is mixed with the food waste that has not been treated for subsequent treatment; VOC gas generated by the food waste can be collected and absorbed by alkali washing or burned in a gas furnace, the heat generated by the combustion is used to preheat the crushed food waste, the gas discharged after alkali washing or burning can meet the emission standards, and the alkali washing waste liquid can be used for subsequent fertilizer preparation; grease or bio-oil generated by the thermal hydrolysis reaction of the food waste can also be recycled; the water phase and solid phase products of the food waste after the thermal hydrolysis reaction have been ultra-high temperature sterilized and can be used for preparing fertilizers, and the alkali washing waste liquid of the VOC gas can also be used for preparing fertilizers.

[0025] Furthermore, the sorted plastic products and metal products can be recycled and reused after cleaning.

[0026] Furthermore, the cleaning waste liquid is used to mix with untreated food waste. The benefit of this is that zero discharge of cleaning waste liquid is achieved. Considering that the cleaning waste liquid has not been treated at high temperature and may still contain residual bacteria and viruses, it is first mixed with untreated food waste, and then hydrolyzed at 350℃ with the materials, and then enters the fertilizer mixing stage after being completely inactivated and disinfected.

[0027] Furthermore, technologies such as oxygen-enriched combustion and staged combustion are used to achieve emission standards.

[0028] Furthermore, the temperature of the thermal hydrolysis reaction is 160-350°C and the pressure is 0.5-20MPa, which can effectively remove viruses, bacteria and insect eggs in the food waste.

[0029] Furthermore, after hydrothermal treatment at 160-200℃, the organic matter in the food waste can be broken and separated into industrial oleic acid, stearic acid or biodiesel, which is an objective chemical reaction process. The added value of industrial oleic acid, stearic acid or biodiesel is higher than that of bio-oil generated at 280℃. Therefore, when extracting valuable components from food waste, first perform "low temperature" separation to extract oleic acid, stearic acid or biodiesel, and then perform "high temperature" separation to extract bio-oil, thereby achieving the maximum resource utilization of waste materials.

[0030] Furthermore, the VOC gas of kitchen waste mainly contains mercaptans, thioamidine and other substances, which can be absorbed by alkaline washing, which is a common operation in this field. The innovation of this scheme lies in the selection of alkaline solution. KOH is used as the alkaline solution. When the absorption is saturated, the potassium-rich liquid produced can be directly used as a potassium source additive in the fertilizer making process, thereby achieving zero discharge of odor treatment waste liquid and realizing resource utilization.

[0031] In summary, the present invention is based on high-temperature thermal hydrolysis technology and optimizes the material flow within the system. While achieving thorough treatment of food waste, no additional emissions of gas, liquid, or solid substances are carried out, truly achieving harmless treatment.

[0032] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0036] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0037] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects are in an "or" relationship.

[0038] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0039] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0040] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0041] The present invention provides a method for harmless treatment of restaurant kitchen waste based on thermal hydrolysis, which adopts the combination of sorting and crushing, VOC gas alkali washing or combustion heating, thermal hydrolysis reaction and fertilizer preparation, so as to achieve harmless treatment of restaurant kitchen waste and improve the efficiency of biomass energy conversion of restaurant kitchen waste.

[0042] See also Figure 1 The present invention discloses a method for harmless treatment of kitchen waste based on thermal hydrolysis, which includes sorting and crushing, indirect preheating, thermal hydrolysis reaction and fertilizer preparation processes, and the specific steps are as follows:

[0043] S1. Sorting and crushing

[0044] After being collected, the food waste is sorted and crushed. The sorted plastic and metal products can be recycled after cleaning. The waste liquid after cleaning is mixed with the untreated food waste for subsequent fertilizer preparation and treatment.

[0045] The particle size of kitchen waste after crushing is 0.1 to 1 mm.

[0046] S2, indirect preheating

[0047] The VOC gas generated by the food waste can be collected and then alkaline washed or burned. The heat generated by the combustion is used to preheat the crushed food waste. The gas discharged after alkaline washing or combustion can meet the emission standards, and the alkaline washing waste liquid can be used for the subsequent preparation of fertilizers.

[0048] The combustion of VOC gas adopts oxygen-enriched combustion, staged combustion and other technologies to achieve standard emission. The high-temperature gas generated after combustion transfers heat to the crushed food waste through the heat exchange surface; the alkaline washing of VOC gas generally uses KOH solution or NaOH solution.

[0049] S3. Thermal hydrolysis reaction

[0050] The kitchen waste is subjected to thermal hydrolysis at 160-350°C to effectively remove viruses, bacteria and insect eggs in the kitchen waste. At the same time, the grease or bio-oil produced after the thermal hydrolysis of the kitchen waste can also be recycled.

[0051] The heating method can be direct heating such as electric heating or fuel oil and gas heating, or indirect heating through intermediate media such as heat transfer oil and water.

[0052] The pressure of the hot hydrolysis reaction of food waste is 0.5~20MPa, and the time ranges from tens of minutes to several hours. The oil separated after the hot hydrolysis reaction at 160~200℃ can be used as industrial oleic acid, stearic acid or to make biodiesel. The bio-oil separated after the high-temperature hot hydrolysis reaction at 280℃ can be used as fuel oil or chemical raw material.

[0053] S4. Fertilizer preparation

[0054] The products of hot hydrolysis of kitchen waste can be used to prepare fertilizers, and the alkaline washing waste liquid of VOC gas can also be used to prepare fertilizers.

[0055] The products of the thermal hydrolysis reaction of food waste and the waste liquid generated during the entire treatment process can be formulated into fertilizers by supplementing the missing elements or substances.

[0056] Fertilizers include national standard foliar fertilizers.

[0057] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0058] Example

[0059] After being collected, the kitchen waste is sorted and crushed by the sorting and crushing device. The sorted plastic and metal products are washed and recycled. The waste liquid after washing is mixed with the untreated kitchen waste for subsequent treatment.

[0060] The VOC gas generated during the entire treatment process of food waste is collected and then treated harmlessly through combustion or alkali washing. The treated VOC gas can achieve standard emission. The heat generated by the combustion of VOC gas can be used to preheat the crushed food waste. The combustion generally adopts clean combustion technologies such as oxygen-enriched combustion and graded combustion. KOH solution or NaOH solution is usually used for alkali washing of VOC gas, and the adsorption effect of activated carbon can also be used for coordinated treatment. The waste liquid after alkali washing is used for subsequent fertilizer preparation.

[0061] The crushed or preheated food waste is heated to the reaction temperature of thermal hydrolysis for reaction. After the thermal hydrolysis reaction, bacteria and other pathogens in the food waste will be completely killed. The oil separated after the thermal hydrolysis reaction at 160-200°C is used as industrial oleic acid, stearic acid, industrial oil or biodiesel. The bio-oil separated after the high-temperature thermal hydrolysis reaction at 280°C is used as fuel oil or chemical raw material.

[0062] The products after the thermal hydrolysis reaction are prepared into national standard foliar fertilizers and other fertilizers by supplementing the missing elements or substances. The alkaline washing waste liquid of VOC gas is also used to prepare fertilizers.

[0063] In summary, the present invention provides a harmless treatment method for food waste based on thermal hydrolysis, which utilizes the combustion of VOC gas generated by food waste to provide heat for crushed food waste, and utilizes the energy of VOC gas while achieving standard emission of gas after combustion; utilizes the alkali washing waste liquid of VOC gas generated by food waste to prepare fertilizer, which achieves standard emission of VOC gas and harmlessness of alkali washing waste liquid, and provides required Na and K elements for fertilizer; utilizes thermal hydrolysis reaction to treat food waste and uses reaction products and waste liquid generated in the treatment process to prepare fertilizer, which achieves sterilization and inactivation of food waste and harmlessness of reaction products and waste liquid.

[0064] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for harmless treatment of kitchen waste based on thermal hydrolysis, characterized in that: The following steps are involved: S1. Sorting and crushing the kitchen waste, collecting the generated VOC gas, washing the sorted plastic products and metal products, recovering the plastics and metals, and mixing the obtained washing waste liquid with the untreated kitchen waste; S2, burning the VOC gas obtained in step S1, using the heat generated by the combustion to preheat the kitchen waste crushed in step S1, and using oxygen-enriched combustion or staged combustion technology to cleanly burn the VOC gas; S3, performing thermal hydrolysis on the kitchen waste after the preheating treatment in step S2 to obtain an oil phase product, a harmless water phase and solid phase product, and VOC gas; S4. Alkali washing is performed on the VOC gas obtained in step S1 and step S3 to obtain alkaline washing waste liquid, and the alkaline washing waste liquid and the harmless water phase and solid phase products obtained in step S3 are used to prepare fertilizer, thereby realizing harmless treatment of food waste based on thermal hydrolysis.

2. The method for harmless treatment of kitchen waste based on thermal hydrolysis according to claim 1, characterized in that: In step S1, the particle size of the crushed kitchen waste is 0.1-1 mm.

3. The method for harmless treatment of kitchen waste based on thermal hydrolysis according to claim 1, characterized in that: In step S3, the temperature of the thermal hydrolysis reaction is 160-350° C. and the pressure is 0.5-20 MPa.

4. The method for harmless treatment of kitchen waste based on thermal hydrolysis according to claim 3, characterized in that: The oil separated after the thermal hydrolysis reaction at 160~200℃ is used to produce industrial oleic acid, stearic acid or biodiesel.

5. The method for harmless treatment of kitchen waste based on thermal hydrolysis according to claim 3, characterized in that: The bio-oil separated after the 280℃ high temperature thermal hydrolysis reaction is used to produce fuel oil or chemical raw materials.

6. The method for harmless treatment of kitchen waste based on thermal hydrolysis according to claim 1, characterized in that: In step S4, alkaline washing is performed using a KOH solution or a NaOH solution.

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