A method for utilizing cow dung hydrothermal resources

Abstract

The present invention belongs to the technical field of resource utilization of livestock and poultry manure, and specifically relates to a method for hydrothermal resource utilization of cow dung. It includes: a hydrothermal treatment process: subjecting cow dung to hydrothermal treatment, and then utilizing the high-pressure environment generated by the hydrothermal treatment to dehydrate the liquid components in the cow dung through filter pressing to obtain hydrothermal charcoal for standby use; a bedding fermentation process: mixing a bedding matrix, a fermentation bacterial agent and the hydrothermal charcoal to obtain a mixed material, and then fermenting to obtain a fermented bedding; a bedding laying process: including a bottom bedding and an upper bedding, wherein the bottom bedding is the hydrothermal charcoal, which is laid on the ground of a cowshed; and the upper bedding is the fermented bedding obtained in the bedding fermentation process, which is laid above the bottom bedding. The method uses the hydrothermal product of cow dung for cow bedding, and the finished bedding has a low moisture content, is thoroughly sterilized and disinfected, has a low cost, and has a short processing time. At the same time, the method can also effectively improve the environment in the shed and keep the cowshed environment clean.

Description

Technical Field

[0001] The invention belongs to the technical field of livestock and poultry manure resource utilization, and specifically relates to a method for hydrothermal resource utilization of cattle manure. Background Art

[0002] The rapid development of large-scale dairy farms has put forward higher requirements for the treatment of manure and sewage in dairy farms. At present, the main ways of utilizing manure and sewage in dairy farms include anaerobic fermentation, composting, and the production of recycled bedding for cow beds. Among them, the production of bedding using manure is an emerging way of utilizing manure resources, which can provide dairy farms with sufficient sources of bedding while solving the problem of manure and sewage treatment in dairy farms. The common method used in the production of existing cow bedding is to first separate the solid and liquid of manure, and then use the solid cow dung as bedding after aerobic fermentation and sterilization, or use the solid cow dung as bedding after anaerobic fermentation. Safety and moisture content are two important indicators for the production of recycled cow bedding for cow beds from solid cow dung, which determine the safety and comfort of subsequent bedding applications. However, in the existing process of using solid cow dung to make cow bedding, there are usually problems such as high cost, long processing time, substandard moisture content of the finished bedding, and incomplete sterilization and disinfection.

[0003] Hydrothermal reaction can be broadly defined as a reaction carried out in high-temperature and high-pressure water (generally at a temperature of 150-600°C and a pressure of 2-50 MPa). The main reaction mechanisms include hydrolysis, dehydration, decarboxylation, polymerization and aromatization. As a new type of biomass resource utilization technology, hydrothermal conversion technology has been widely studied by scientific researchers. Under high temperature and high pressure conditions, the water in manure is in a subcritical state, with a high free ionization constant and a low dielectric constant, which makes water as a reaction solvent have a strong solubility and penetration ability. During the reaction, the microbial cells are broken, and the organic matter (protein, fat, carbohydrate) in the cells is further hydrolyzed into small molecules. The cell-bound water is released, which improves the dehydration performance of manure.

[0004] At present, the application of hydrothermal dehydration and sterilization technology in municipal sludge dehydration is relatively mature. The Porteous process uses steam to heat treat primary sludge and secondary sedimentation tank sludge to promote sludge dehydration performance. The solid content of dehydrated sludge increases from 20% to 40%; the Zimpro process uses compressed air as an oxidant to wet oxidize the sludge, with the aim of completely sterilizing, fully deodorizing, and facilitating dehydration of the sludge; the Cambi process uses high-pressure steam to pre-treat industrial sludge for anaerobic digestion to decompose cell structures and organic matter, providing easily digestible raw materials for anaerobic reactions. Summary of the invention

[0005] In view of the problems existing in the existing technology of using cow dung to make cow bedding materials, such as incomplete sterilization and disinfection, high processing cost and long processing time, the present invention proposes a method for using hydrothermal technology to treat cow dung, improve the dehydration rate of dung, enhance the sterilization effect, and use the hydrothermal product as a hydrothermal resource of cow dung for cow bedding materials. This method can also effectively improve the environment in the cow shed and keep the cow shed environment clean.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] A method for utilizing cow dung hydrothermal resources, comprising:

[0008] Hydrothermal treatment process: subjecting the cow dung to hydrothermal treatment, and then utilizing the high pressure environment generated by the hydrothermal treatment to dehydrate the liquid components in the cow dung through filter pressing to obtain hydrothermal charcoal for standby use; the hydrothermal treatment preferably adopts a low-temperature hydrothermal treatment process under anaerobic conditions, the main purpose of which is to kill pathogenic bacteria in the dung and provide clean laying materials for subsequent cow mattresses. At the same time, the high-pressure hydrothermal treatment is more conducive to the dehydration effect of the dung and shortens the subsequent dehydration process;

[0009] Litter fermentation process: mixing a litter matrix with a fermentation agent to obtain a mixed material; adding the hydrothermal charcoal into the mixed material, and then fermenting to obtain a fermented litter;

[0010] The bedding laying process includes a bottom layer of bedding and an upper layer of bedding. The bottom layer of bedding is the hydrothermal charcoal, which is laid on the floor of the cowshed and is mainly used to keep the cowshed bedding dry and absorb the pollutants in the cowshed manure to make the cowbed bedding cleaner. The upper layer of bedding is the fermented bedding obtained in the bedding fermentation process and is laid on top of the bottom layer of bedding.

[0011] Preferably, in the hydrothermal treatment process, before the hydrothermal treatment, the moisture content of the cow dung is adjusted to 70-90%; the temperature of the hydrothermal treatment is 160°C-220°C, the pressure is 1MPa-2MPa, and the time is 0.5h-1h. The above hydrothermal treatment conditions can effectively break up the cell structure, separate the bound water in the dung, and increase the dehydration rate to 75%, reducing the dehydration process flow. At the same time, the high temperature and high pressure environment can effectively achieve the sterilization effect and prevent secondary pollution.

[0012] Preferably, in the hydrothermal treatment step, the filter medium used in the filter press comprises a filter press cover and a filter press plate that are in contact with each other;

[0013] The filter press cover is in a groove shape, comprising an annular cover wall and a cover top sealed at one end of the cover wall, the surface of the cover wall has a plurality of first holes, and the center of the cover top is provided with a central hole connected to the outlet of the hydrothermal treatment product;

[0014] The filter press plate is cylindrical and matches the shape of the groove. The plate surface of the filter press plate close to the filter press cover has a plurality of second holes. The cylindrical surface of the filter press plate has a plurality of third holes. The second holes are connected to the third holes. The plate surface of the filter press plate away from the filter press cover is connected to a pressure device.

[0015] The diameters of the first hole, the second hole and the third hole are 1 to 2 mm.

[0016] The operating principle of the above-mentioned filter medium is: the filter cover and the filter plate are in contact with each other, and a certain pressure is applied to the contact surface through the pressure device connected to the filter plate. The high-pressure material in the hydrothermal reactor enters between the filter cover and the top and plate surface of the filter plate through the central hole on the filter cover, and the liquid phase in the high-pressure material enters the filter plate through the first hole, and then is discharged through the second hole on the cylindrical surface of the filter plate and the first hole on the cover wall surface of the filter cover in turn; the solid phase in the high-pressure material is retained between the filter cover and the filter plate, thereby achieving solid-liquid separation. At the same time, the pressure device is designed to be pressure-adjustable, and the pressure is lower than the pressure in the reactor.

[0017] The present invention utilizes the above-mentioned specific filter medium to realize the filter pressure separation of the slurry. The pressure source is the high-pressure system generated by the hydrothermal reactor, which can reduce the energy consumption of the system, save operating costs, and achieve a high dehydration rate. At the same time, it can also effectively prevent the blockage of the discharge port, avoid clogging the filter medium, and increase the filter pressure speed.

[0018] Further preferably, the pressure device is a spring. The spring pressure is a reverse force, which is consistent with the pressure of the hydrothermal kettle in real time, thereby effectively improving the solid-liquid separation effect of the filter press and being able to cope with different hydrothermal outlet pressures.

[0019] Further preferably, the lower sector of the missing portion of the top of the filter press cover;

[0020] The plate surface of the filter press plate close to the filter press cover is provided with a fan-shaped protrusion, the shape of the fan-shaped protrusion is consistent with the shape of the lower fan-shaped protrusion of the cover top, and the thickness is consistent with the thickness of the cover top. The filter press cover is a round cover structure with the lower fan-shaped protrusion missing, which can easily remove the solid hydrothermal carbon remaining in the filter press cover after filtration and is also easy to clean.

[0021] In another preferred embodiment, the filter press cover and the filter press plate are made of 304 stainless steel.

[0022] Preferably, in the bedding fermentation step, the bedding matrix is ​​selected from at least one of sawdust, rice husks and rice bran.

[0023] Preferably, in the bedding fermentation process, the amount of the hydrocharcoal added is 5% to 10% based on the mass of the bedding matrix. When the upper bedding is decomposed, a certain amount of hydrocharcoal is added as an additive, which can effectively improve the microbial activity, porosity, air permeability, conductivity and other indicators, thereby improving the decomposition efficiency.

[0024] Preferably, in the bedding fermentation process, the fermentation time is 8 to 10 hours, the moisture content of the fermentation raw materials is controlled to be 60 to 65%, and the fermentation temperature is 40°C to 60°C.

[0025] Preferably, in the bedding laying process, the thickness of the bottom bedding is 3 to 5 cm. The present invention creatively directly uses hydrothermal charcoal as the bottom bedding, and it is found that it can play the role of adsorption, deodorization, drying, etc., thereby effectively improving the environment in the barn and keeping the cowshed clean.

[0026] Preferably, in the bedding laying process, a grid plate is first laid on the floor of the cowshed, and then the hydrothermal charcoal is filled into the holes of the grid plate to obtain the bottom bedding. The biochar bottom bedding is fixed with a grid-shaped plate to prevent the biochar from being lost and avoid dust.

[0027] Preferably, in the padding laying process, the thickness of the upper padding is 15 to 20 cm.

[0028] Further preferably, fresh fermentation bedding is added every day to keep the thickness of the upper bedding at 15 to 20 cm.

[0029] Preferably, in the bedding laying process, after each batch of cattle is released from the market, the upper bedding is mixed with cow dung and reused after the hydrothermal treatment process. The bedding in the shed of the present invention can be recycled and hydrothermally carbonized to achieve resource utilization.

[0030] The beneficial effects of the present invention are:

[0031] The method for utilizing cow dung hydrothermal resources provided by the present invention uses the cow dung hydrothermal products for cow bedding. The finished bedding has low moisture content, is thoroughly sterilized and disinfected, has low cost, and takes short processing time. At the same time, the method can also effectively improve the environment in the cowshed and keep the cowshed clean. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the prior art description in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1The present invention is a schematic flow diagram of the method for hydrothermal resource utilization of cow dung; in the figure: ①, hydrothermal treatment process; ②, bedding fermentation process; ③, bedding laying process.

[0034] Figure 2 This is a schematic diagram of the structure of the bedding material of the present invention; in the figure: 11, biochar bottom bedding material; 22, upper fermentation bedding material.

[0035] Figure 3 Schematic diagram of the hydrothermal high-pressure filter press structure used in Example 1; in the figure: 1, hydrothermal product outlet filter press; 1-1, cover wall; 1-2, cover top; 1-3, first hole; 1-4, center hole; 2, spring filter press; 2-1, second hole; 2-2, third hole; 2-3, spring; 2-4 fan-shaped raised portion. DETAILED DESCRIPTION

[0036] The present invention provides a method for utilizing cow dung hydrothermal resources. In a preferred embodiment, Figure 1 As shown, there are three processes: ① hydrothermal treatment process, ② bedding fermentation process, and ③ bedding laying process.

[0037] The main process flow is:

[0038] Process ①: mainly includes the steps of hydrothermal treatment, pressure relief dehydration, and solid phase utilization. Among them, the cow dung is first subjected to hydrothermal treatment at a temperature of 160℃-220℃, a reaction pressure of 1MPa-2MPa, and a residence time of 0.5h-1h. After the high temperature and high pressure hydrothermal reaction, the feces microbial cells are broken, the cell bound water is released, and the dehydration performance is improved. Pressure relief dehydration refers to directly connecting a filter press type solid-liquid separation system to the rear end of the hydrothermal reaction system, and using the high-pressure fluid after the hydrothermal reaction to achieve filter press separation of the slurry, thereby reducing system energy consumption and saving operating costs. The solid phase utilization step is to use a portion of the hydrothermal solid phase product (i.e., hydrothermal charcoal) after the filter press as a composting additive for the upper layer of bedding, and the other portion is used to prepare the biochar bottom layer of bedding.

[0039] Process ②: mainly includes the steps of mixing ingredients, composting and preparing upper bedding. The mixed ingredients can be made of sawdust, rice husks, rice bran, fermentation bacteria and other raw materials in a certain proportion, and the hydrothermal solid phase product is added as an additive at a ratio of 5%-10%, and then fermented to obtain fermented bedding. The moisture content of the compost is controlled to 60-65%, and the porous characteristics of hydrothermal charcoal are used to improve the activity of microorganisms and conductivity, thereby improving the fermentation effect.

[0040] Process ③: mainly includes the steps of laying and recycling the litter in the house, such as Figure 2As shown, the bedding in the shed is mainly composed of the upper fermentation bedding 22 and the biochar bottom bedding 11. The biochar bottom bedding 11 is fixed with a grid-shaped plate. The grid plate is a 2mm*2mm square with a depth of 5mm to prevent the loss of biochar. The upper fermentation bedding 22 is directly laid on the upper end of the biochar bottom bedding 11. The laying thickness of the upper fermentation bedding 22 is 15cm-20cm, and the laying thickness of the biochar bottom bedding 11 is 3-5cm. The fermentation bedding is replenished every day to ensure the thickness of the upper fermentation bedding 22. After the cattle are released from the market, the remaining upper fermentation bedding 22 is hydrothermally reacted with the cow dung to realize the recycling of the cattle bedding.

[0041] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Without departing from the spirit and substance of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention are within the scope of the present invention.

[0042] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. All reagents or instruments without manufacturer specified are conventional products that can be purchased through regular channels.

[0043] like Figure 3 As shown, the filter medium used in the filter press system in the following embodiments includes a filter press cover 1 and a filter press plate 2 which are assembled and contacted with each other;

[0044] The filter press cover 1 is in the shape of a groove, and comprises an annular cover wall 1-1 and a cover top 1-2 sealed at one end of the cover wall, the surface of the cover wall has a plurality of evenly distributed first holes 1-3, and the center of the cover top is provided with a central hole 1-4 connected to the outlet of the hydrothermal treatment product;

[0045] The filter press plate 2 is cylindrical and matches the shape of the groove. The plate surface of the filter press plate close to the filter press cover has a plurality of second holes 2-1. The cylindrical surface of the filter press plate has a plurality of evenly distributed third holes 2-2. The second holes are connected to the third holes. The plate surface of the filter press plate away from the filter press cover is connected to a spring 2-3. The spring pressure is a reverse force and is consistent with the pressure of the hydrothermal kettle in real time.

[0046] The diameters of the first hole, the second hole, and the third hole are 1.5 mm;

[0047] Furthermore, the lower sector of the missing portion of the top of the filter press cover (with an arc of 120 degrees);

[0048] The plate surface of the filter press plate close to the filter press cover is provided with a fan-shaped protrusion 2-4, the shape of the fan-shaped protrusion is consistent with the shape of the missing lower fan-shaped protrusion of the cover top, and the thickness is consistent with the thickness of the cover top.

[0049] Example 1

[0050] A method for utilizing cow dung hydrothermal resources, comprising the following steps:

[0051] The manure in the cowshed is transported to the hydrothermal reaction system through a screw pump or other conveying mechanism, and the hydrothermal reaction temperature is adjusted to 180°C, the reaction pressure is 2MPa, and the residence time is controlled to 1h. The cowshed manure is subjected to hydrothermal reaction treatment. The hydrothermal slurry after treatment is then separated into solid and liquid by a filter press system to obtain solid-phase hydrothermal charcoal. The hydrothermal charcoal has a moisture content of about 25%. Part of the hydrothermal charcoal is mixed with sawdust, rice husks, rice bran, fermentation bacteria and other raw materials to prepare the upper fermentation bedding. The hydrothermal charcoal addition ratio is 10%. The liquid phase obtained after the hydrothermal slurry is filtered by pressure to adjust the moisture content of the fermentation bedding to 60%, and the fermentation time is 12 hours. Another part of the hydrothermal charcoal is fixed with a grid-shaped plate to prepare the biochar bottom bedding. The grid plate is a 2mm*2mm square with a depth of 5mm. The biochar bottom layer bedding is laid on the floor of the cowshed with a thickness of 4 cm, and the fermented upper layer bedding is laid on the top of the biochar bottom layer bedding with a thickness of 18 cm to achieve the preparation of renewable cattle bedding. After the cattle are slaughtered, the remaining upper layer bedding is subjected to hydrothermal reaction together with cow dung to achieve the recycling of cattle bedding.

[0052] The above embodiments are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineers and technicians in the field should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for utilizing cow dung hydrothermal resources, characterized in that: include: Hydrothermal treatment process: subjecting the cow dung to hydrothermal treatment, and then utilizing the high pressure environment generated by the hydrothermal treatment to dehydrate the liquid components in the cow dung through filter pressing to obtain hydrothermal charcoal for standby use; Litter fermentation process: mixing the litter matrix, fermentation bacteria and the hydrothermal charcoal to obtain a mixed material, and then fermenting to obtain a fermented litter; In the bedding fermentation process, the amount of the hydrothermal charcoal added is 5% to 10% based on the mass of the bedding matrix; The bedding laying process includes a bottom bedding layer and an upper bedding layer. The bottom bedding layer is the hydro-heated charcoal, which is laid on the floor of the cowshed. The upper bedding layer is the fermented bedding obtained in the bedding fermentation process, which is laid on top of the bottom bedding layer.

2. The method for utilizing cow dung hydrothermal resources according to claim 1, characterized in that: In the hydrothermal treatment process, before the hydrothermal treatment, the moisture content of the cow dung is adjusted to 70-90%; the temperature of the hydrothermal treatment is 160° C.-220° C., the pressure is 1 MPa-2 MPa, and the time is 0.5 h-1 h.

3. The method for utilizing cow dung hydrothermal resources according to claim 1 or 2, characterized in that: In the hydrothermal treatment process, the filter medium used in the filter press includes a filter press cover and a filter press plate that are in contact with each other; The filter press cover is in a groove shape, comprising an annular cover wall and a cover top sealed at one end of the cover wall, the surface of the cover wall has a plurality of first holes, and the center of the cover top is provided with a central hole connected to the outlet of the hydrothermal treatment product; The filter press plate is cylindrical and matches the shape of the groove. The plate surface of the filter press plate close to the filter press cover has a plurality of second holes. The cylindrical surface of the filter press plate has a plurality of third holes. The second holes are connected to the third holes. The plate surface of the filter press plate away from the filter press cover is connected to a pressure device. The diameters of the first hole, the second hole and the third hole are 1 to 2 mm.

4. The method for utilizing cow dung hydrothermal resources according to claim 3, characterized in that: The lower sector of the missing portion of the top of the filter press cover; The plate surface of the filter press plate close to the filter press cover is provided with a sector-shaped protrusion, the shape of the sector-shaped protrusion is consistent with the shape of the missing lower sector of the cover top, and the thickness is consistent with the thickness of the cover top.

5. The method for utilizing cow dung hydrothermal resources according to any one of claims 1 to 4, characterized in that: In the bedding fermentation process, the fermentation time is 8 to 10 hours, the moisture content of the fermentation raw materials is controlled at 60 to 65%, and the fermentation temperature is 40°C to 60°C.

6. The method for utilizing cow dung hydrothermal resources according to any one of claims 1 to 5, characterized in that: In the padding laying process, the thickness of the bottom padding is 3 to 5 cm.

7. The method for utilizing cow dung hydrothermal resources according to any one of claims 1 to 6, characterized in that: In the bedding laying process, firstly, a grid plate is laid on the ground of the cowshed, and then the hydrothermal charcoal is filled into the holes of the grid plate to obtain the bottom bedding.

8. The method for utilizing cow dung hydrothermal resources according to any one of claims 1 to 7, characterized in that: In the padding laying process, the thickness of the upper padding is 15 to 20 cm.

9. The method for utilizing cow dung hydrothermal resources according to any one of claims 1 to 7, characterized in that: During the bedding laying process, fresh fermented bedding is added every day to keep the thickness of the upper bedding at 15 to 20 cm.

10. The method for utilizing cow dung hydrothermal resources according to any one of claims 1 to 9, characterized in that: In the bedding laying process, after each batch of cattle is released from the market, the upper bedding is mixed with cow dung and reused after the hydrothermal treatment process.

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