A method for preparing an organic fertilizer

Abstract

The application discloses a preparation method of organic fertilizer, and relates to the technical field of organic fertilizer production, and comprises the following steps: S1, pretreating organic raw materials; S2, inoculating fermentation inoculums into the pretreated organic raw materials to form a heap for aerobic fermentation; and S3, in the process of aerobic fermentation, the temperature of each part of the heap is monitored in real time, the center temperature of the heap, the peripheral temperature of the heap and the temperature difference between the center and the periphery of the heap are taken as control parameters, a heat-carrying medium circulation mode is adopted, external heat is conducted to the heap, internal heat of the heap is absorbed and migrated and released in a variable frequency operation mode, and the temperature field of the heap is actively adjusted; the method takes the center and peripheral temperatures of the heap and the temperature difference between the center and the periphery as control parameters, adopts the heat-carrying medium circulation to cooperate with three modes of temperature rising, temperature balancing and temperature falling, actively adjusts the temperature field of the heap, solves the problem of uneven temperature distribution in traditional aerobic fermentation, accelerates the start-up of temperature rising circulation, reduces the temperature difference through temperature balancing circulation, and prevents over-temperature through temperature falling circulation.

Description

Technical Field

[0001] This invention relates to the field of organic fertilizer production technology, and specifically to a method for preparing organic fertilizer. Background Technology

[0002] Aerobic fermentation is the core process in the preparation of organic fertilizer. Changes in the temperature field of the compost pile directly affect the activity of microorganisms and the degradation efficiency of organic matter. At present, the heating stage of aerobic fermentation mainly relies on the heat generated by the metabolism of the material itself, while the cooling stage mostly adopts turning, ventilation or natural heat dissipation to achieve temperature regulation.

[0003] Chinese invention patent CN 111393203 B discloses a static composting heat recovery and utilization system for agricultural and forestry organic solid waste. The system has a leachate tank installed below the fermentation chamber, and the bottom ventilation space is connected to the leachate tank through a pipeline. A spraying device is arranged above the material pile in the fermentation chamber. The fermentation chamber and the partition wall heat exchanger are connected by an air supply pipe and a return air pipe. A circulating fan is arranged on the return air pipe, and the air outlet of the return air pipe is located in the bottom ventilation space. A fresh air duct is also connected to the return air pipe between the partition wall heat exchanger and the circulating fan. The partition wall heat exchanger is connected to the heat use system through a pipeline to form a closed liquid or gas flow loop, which maximizes the recovery and utilization of latent heat and sensible heat generated during fermentation.

[0004] Existing technologies can only achieve unidirectional heat transfer from the pile to the external environment. They cannot redistribute and transfer internal heat based on temperature differences in different parts of the pile. When the temperature at the center of the pile is higher than that at the periphery, the excess heat at the center cannot be actively transferred to the periphery to balance the temperature field. When the temperature of the pile is insufficient during the fermentation start-up stage, external heat cannot be introduced into the pile for auxiliary heating. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing organic fertilizer to solve the problem of uneven temperature distribution inside the compost pile in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing organic fertilizer, comprising:

[0007] S1. Pre-treatment of organic raw materials;

[0008] S2. Inoculate the pretreated organic raw materials with fermentation agents to form a pile for aerobic fermentation;

[0009] S3. During the aerobic fermentation process, the temperature of each part of the pile is monitored in real time. Taking the temperature at the center of the pile, the temperature at the periphery of the pile, and the temperature difference between the center and the periphery of the pile as control parameters, a heat-carrying medium circulation method is adopted to realize the conduction of external heat to the pile and the absorption, migration and release of the internal heat of the pile in a variable-frequency operation mode, so as to actively regulate the temperature field of the pile;

[0010] S4. The organic fertilizer after aerobic fermentation is subjected to decomposition maturity treatment.

[0011] Further, said circulation modes include a temperature rise circulation, a uniform circulation and a temperature reduction circulation;

[0012] Said temperature rise circulation conducts heat outside the pile to the pile, which includes external temperature control, peripheral heat release and pile core heat exchange. The heat-carrying medium is heated up externally, releases heat at the periphery of the pile and then performs heat exchange with the pile core to conduct heat to the pile core, and finally flows back to be heated up externally to continue the circulation;

[0013] Said uniform circulation absorbs the heat inside the pile and conducts it to the periphery of the pile, which includes pile core heat exchange, peripheral heat release and external temperature control. The heat-carrying medium performs heat exchange with the pile core, absorbs heat from the pile core, releases heat at the periphery of the pile, then flows back to the pile core after being cooled externally to re-absorb heat and continue the circulation;

[0014] Said temperature reduction circulation absorbs the heat inside the pile and conducts it to the outside of the pile, which includes pile core heat exchange and cyclic migration. The heat-carrying medium performs heat exchange with the pile core, absorbs heat from the pile core and then conducts the heat to the outside of the pile through cyclic migration, and then performs heat exchange with the pile core to continue the circulation.

[0015] Further, the average temperature value of each temperature measuring point in the central area of the pile is taken as the pile center temperature Tc, the weighted average temperature value of each temperature measuring point at the periphery of the pile is taken as the pile periphery temperature Tw, ΔT=Tc-Tw is taken as the temperature difference between the pile center and the pile periphery, and the start threshold T1 and the regulation threshold T2 are set according to the type of organic fertilizer;

[0016] When Tc<T1, said temperature rise circulation is started;

[0017] When ΔT>T2, said uniform circulation is started;

[0018] When Tw>T1, said temperature reduction circulation is started;

[0019] The priority of said temperature rise circulation is higher than that of said temperature reduction circulation, and the priority of said temperature reduction circulation is higher than that of said uniform circulation.

[0020] Furthermore, the circulation method uses a circulation pump as power, and the variable frequency operation mode is a three-stage variable frequency operation mode. The frequency of the circulation pump can be adjusted in three levels, and the shift thresholds T3 and T4 are set according to the type of organic fertilizer, with T3 being the highest value. <T4;

[0021] When T2 < ΔT ≤ T3, the circulating pump operates at 30% to 50% of its rated frequency;

[0022] When T3 < ΔT ≤ T4, the circulating pump operates at 60% to 80% of its rated frequency;

[0023] When ΔT>T4, the circulating pump operates at 100% of its rated frequency;

[0024] When Tw>T1, the cooling cycle is started, and the circulation pump operates at 100% of its rated frequency.

[0025] Furthermore, the core heat exchange adopts a method of pre-setting heat exchange pipelines in the core, and the heat exchange pipelines are spiral hollow coils.

[0026] Furthermore, the external temperature control adopts a water bath temperature control single tube method, wherein the single tube is a water bath heat exchange tube used to heat and cool the heat transfer medium;

[0027] The external heat release adopts the method of pre-setting bottom heat release branches and side wall heat release branches in the reactor body. The bottom heat release branch is a comb-shaped pipe located at the bottom of the reactor body, and the side wall heat release branch is a pipe arranged back and forth along the side wall of the reactor body.

[0028] The single pipe, the bottom heat release branch, the side wall heat release branch, the heat exchange pipeline, and the circulation pump are connected in sequence to form a loop.

[0029] Furthermore, the circulating migration adopts a water bath temperature-controlled dual-pipe method. The dual-pipe consists of two parallel water bath heat exchange pipes used to directly discharge the heat of the heat transfer medium to the outside of the reactor body, and their two ends are respectively connected to the heat exchange pipeline and the circulating pump to form a loop.

[0030] Furthermore, the heat transfer medium is water.

[0031] Furthermore, the pretreatment includes dehydration, crushing, impurity removal and screening, and adjustment of the carbon-nitrogen ratio.

[0032] Compared with existing technologies, the present invention provides an organic fertilizer preparation method that uses the temperature of the center and periphery of the pile and the temperature difference between them as control parameters. Through the circulation of heat transfer medium and the combination of three modes of heating, equalization and cooling, the temperature field of the pile is actively regulated, which solves the problem of uneven temperature distribution in traditional aerobic fermentation. The heating cycle accelerates the start-up, the equalization cycle reduces the temperature difference, and the cooling cycle prevents overheating. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0034] Figure 1 This is a schematic diagram of the overall process provided for an embodiment of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] As attached Figure 1 As shown:

[0037] Example 1:

[0038] This embodiment uses a mixture of livestock and poultry manure and straw as organic raw materials to prepare organic fertilizer. The specific steps are as follows.

[0039] In this invention, the core refers to the internal region at a depth of at least 30cm from the surface of the reactor body, and the periphery refers to the region at a depth of 10cm-25cm from the surface of the reactor body.

[0040] Fresh cow dung is mixed with corn stalks crushed to a length of 1-3 cm at a mass ratio of 3:1. The moisture content of the mixture is adjusted to 55%-60%, and the carbon-nitrogen ratio is adjusted to 25:1-30:1. Stones, metals and other impurities are removed.

[0041] Inoculate the pretreated organic raw materials with 0.5% of the material mass of aerobic composting fermentation agent, mix evenly, and pile into a 5m×2m×1.5m windrow pile. The fermentation agent can be an organic material composting agent with registration certificate number (2005) (0197).

[0042] Three temperature measuring points are evenly arranged in the central area of ​​the reactor body, and the average temperature is taken as the central temperature Tc. Six temperature measuring points are evenly arranged 20cm away from the surface of the reactor body on the outer perimeter, and the weighted average temperature is taken as the outer perimeter temperature Tw. The weighting coefficient is determined according to the heat dissipation area and heat dissipation conditions of each part. Specifically, the two sides each account for 0.25, the top surface accounts for 0.2, and the bottom surface accounts for 0.3. ΔT=Tc-Tw is used as the temperature difference between the center and the outer perimeter of the reactor body. The start-up threshold T1=50℃ and the adjustment threshold T2=15℃ are set.

[0043] When Tc<T1, it indicates that the heat is insufficient in the fermentation initiation stage, the temperature rise cycle is started, water with a relatively large specific heat capacity is used as the heat-carrying medium, and a circulating pump is used as the power source;

[0044] The specific path of the temperature rise cycle is as follows: the heat-carrying medium is first heated to 55-60°C through a water-bath temperature-controlled single pipe, then flows through the bottom heat release branch and the side wall heat release branch on the periphery of the pile, that is, the comb-tooth-shaped pipeline arranged at the bottom of the pile and the pipeline arranged in a bent and reciprocating manner along the side wall of the pile, releases heat at the periphery of the pile and then enters the spiral hollow coil pre-arranged in the pile core for heat exchange to transfer heat to the pile core, and finally flows back to the water-bath temperature-controlled single pipe to continue the heating cycle. The circulating pump operates at 50% of the rated frequency, and the temperature rise cycle continues until Tc≥55°C. The comb-tooth-shaped pipeline, the bent and reciprocating arranged pipeline and the spiral hollow coil can expand the heat exchange area and improve the heat exchange efficiency;

[0045] After the temperature of the pile naturally drops below 40°C, the materials are moved out for decomposition, and the decomposition time is 15-20 days, to obtain the organic fertilizer product.

[0046] Working principle: Real-time monitoring of the temperature at the center and the periphery of the pile is carried out. When the center temperature is lower than the initiation threshold T1, the temperature rise cycle is started, the heat-carrying medium is heated externally, so that it flows through the periphery of the pile and the pile core sequentially along the pipelines, actively conveying external heat to the interior of the pile, accelerating the temperature rise of the pile core to a suitable fermentation temperature, thereby solving the problem of slow temperature rise in low-temperature seasons or at the initial stage of fermentation.

[0047] Second Embodiment:

[0048] In this embodiment, the mixed material of pig manure and rice husk is used as the organic raw material to prepare organic fertilizer, and the specific steps are as follows.

[0049] Fresh pig manure and rice husk crushed to a length of 0.1-0.2 cm are mixed at a mass ratio of 4:1, the moisture content of the mixed material is adjusted to 55%-65%, the carbon-nitrogen ratio is adjusted to 20:1-28:1, and impurities such as stones and metals therein are removed;

[0050] The aerobic composting fermentation bacterial agent is inoculated into the pretreated organic raw material at 0.8% of the material mass, stirred uniformly and then piled into a windrow-type pile of 6m×2.5m×1.8m. The fermentation bacterial agent can adopt the organic material decomposing agent with the registration certificate number of Microbial Fertilizer (2010) No. 0662;

[0051] The arrangement of temperature measuring points and the weighting method are the same as those in the first embodiment. The average temperature value of each temperature measuring point in the central area of the pile is taken as the pile center temperature Tc, the weighted average temperature value of each temperature measuring point on the periphery of the pile is taken as the pile periphery temperature Tw, ΔT=Tc-Tw is taken as the temperature difference between the pile center and the pile periphery, the initiation threshold T1=50°C and the adjustment threshold T2=15°C are set, and the gear shift thresholds T3=20°C and T4=30°C are set at the same time;

[0052] When Tc≥55℃ and ΔT>T2, the balancing cycle is initiated;

[0053] The specific path of the balanced circulation is as follows: The heat transfer medium first flows through the spiral hollow coil pre-installed in the reactor core, exchanges heat with the reactor core, and absorbs excess heat from the core. Then it flows through the bottom heat release branch and sidewall heat release branch around the reactor body, releases heat on the reactor body periphery, and then flows back to the reactor core to absorb heat again after being cooled by a single tube with water bath temperature control, forming a circulation. The spiral hollow coil, comb-shaped pipes, and the bend-and-reciprocate arrangement of the pipes can expand the heat exchange area and improve the heat exchange efficiency. According to the specific value of ΔT, the circulation pump operates in a three-stage variable frequency mode:

[0054] When 15℃ < ΔT ≤ 20℃, the circulating pump operates at 40% of its rated frequency;

[0055] When 20℃ < ΔT ≤ 30℃, the circulating pump operates at 70% of its rated frequency;

[0056] When ΔT>30℃, the circulating pump operates at 100% of its rated frequency.

[0057] Through balanced circulation, excess heat in the reactor core is actively transferred to the periphery of the reactor body, reducing the temperature difference between the center and the periphery of the reactor body and making the temperature field of the reactor body more uniform.

[0058] After the temperature of the pile naturally drops below 40°C, the material is removed for composting. The composting time is 15 to 20 days, and the organic fertilizer product is obtained.

[0059] Working principle: When the reactor enters the high-temperature fermentation stage, the core temperature is too high while the periphery temperature is relatively low, and the temperature difference ΔT between the two exceeds the set adjustment threshold T2. The equilibrium circulation is started. The heat transfer medium flows through the core spiral coil to absorb the excess heat, and then flows to the bottom and side wall heat release branches of the reactor periphery to release the heat. This realizes the active transfer of heat from the core to the periphery of the reactor, reduces the temperature difference between the core and the periphery, and makes the temperature field of the reactor tend to be uniform.

[0060] The circulating pump is adjusted in three stages according to the temperature difference: the greater the temperature difference, the higher the pump speed and the faster the heat transfer. When the temperature difference falls back to within the threshold, the balanced circulation stops.

[0061] Example 3:

[0062] This embodiment uses a mixture of chicken manure and sawdust as organic raw materials to prepare organic fertilizer. The specific steps are as follows.

[0063] Fresh chicken manure and sawdust are mixed at a mass ratio of 2:1. The moisture content of the mixture is adjusted to 50% to 60%, and the carbon-nitrogen ratio is adjusted to 25:1 to 30:1. Stones, metals and other impurities are removed.

[0064] Inoculate the pretreated organic raw materials with aerobic composting fermentation agent at 0.6% of the material mass, mix evenly, and then pile into a 4m×2m×1.5m windrow pile. The fermentation agent can be an organic material composting agent with registration certificate number (2011) (0783).

[0065] The temperature measurement point arrangement and weighting method are the same as in Example 1. Based on the type of organic fertilizer used in this example, the starting threshold T1 is set to 50℃.

[0066] When Tw>T1, it indicates that the overall temperature of the reactor is too high and forced cooling is required, so a cooling cycle should be started.

[0067] The specific path of the cooling cycle is as follows: The heat transfer medium first flows through the spiral hollow coil pre-installed in the reactor core, exchanges heat with the reactor core and absorbs heat from the reactor core. Then, the heat is discharged to the cooling medium outside the reactor body through one of the water bath temperature-controlled double tubes. The cooled heat transfer medium then flows back to the reactor core through the other of the water bath temperature-controlled double tubes to exchange heat with the reactor core and continue the cycle. The circulation pump runs at 100% full speed at the rated frequency to quickly remove heat from the reactor body with maximum heat exchange efficiency. The spiral hollow coil can expand the heat exchange area and improve the heat exchange efficiency.

[0068] After the temperature of the pile drops below 45°C, the material is removed for composting, which takes 15 to 20 days, to obtain organic fertilizer.

[0069] Working principle: When the overall temperature of the reactor body is too high and the external temperature Tw exceeds the set adjustment threshold T2, the cooling cycle is started. After the heat transfer medium absorbs heat through the core spiral coil, it is directly discharged to the outside of the reactor body through the external water bath temperature control dual pipe. The cooled heat transfer medium flows back to the core to continue absorbing heat, forming a cycle. The circulation pump runs at 100% rated frequency to achieve maximum heat exchange efficiency and quickly force the excess heat inside the reactor body to be removed.

[0070] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for preparing organic fertilizer, characterized in that, comprising: S1. Pretreating organic raw materials; S2. Inoculating the pretreated organic raw materials with a fermentation bacterial agent to form a pile for aerobic fermentation; S3. During the aerobic fermentation process, monitoring the temperature of each part of the pile in real time, taking the pile center temperature, the pile periphery temperature, and the temperature difference between the pile center and the pile periphery as control parameters, adopting a heat-carrying medium circulation mode to realize the conduction of external heat to the pile and the absorption, migration and release of the internal heat of the pile in a variable-frequency operation mode, so as to actively adjust the temperature field of the pile; S4. Decomposing the organic fertilizer after aerobic fermentation.

2. The method for preparing organic fertilizer according to claim 1, characterized in that, Said circulation mode includes a temperature-raising circulation, a balancing circulation and a temperature-lowering circulation; Said temperature-raising circulation conducts the heat outside the pile to the pile, which includes external temperature control, peripheral heat release and pile core heat exchange. The heat-carrying medium is heated externally, releases heat at the periphery of the pile, then performs heat exchange with the pile core to conduct heat to the pile core, and finally flows back to be heated externally to continue the circulation; Said balancing circulation absorbs the heat inside the pile and conducts it to the periphery of the pile, which includes pile core heat exchange, peripheral heat release and external temperature control. The heat-carrying medium performs heat exchange with the pile core, absorbs heat from the pile core, releases heat at the periphery of the pile, then flows back to the pile core after external cooling to re-absorb heat and continue the circulation; Said temperature-lowering circulation absorbs the heat inside the pile and conducts it to the outside of the pile, which includes pile core heat exchange and cyclic migration. The heat-carrying medium performs heat exchange with the pile core, absorbs heat from the pile core, conducts the heat to the outside of the pile through cyclic migration, and then performs heat exchange with the pile core to continue the circulation.

3. The method for preparing organic fertilizer according to claim 2, characterized in that, The average value of the temperatures of all temperature measuring points in the central area of the pile is taken as the pile center temperature Tc, the weighted average value of the temperatures of all temperature measuring points at the periphery of the pile is taken as the pile periphery temperature Tw, ΔT=Tc-Tw is taken as the temperature difference between the pile center and the pile periphery, and the start threshold T1 and the adjustment threshold T2 are set according to the type of organic fertilizer; When Tc<T1, start said temperature-raising circulation; When ΔT>T2, start said balancing circulation; When Tw>T1, start said temperature-lowering circulation; The priority of said temperature-raising circulation is higher than that of said temperature-lowering circulation, and the priority of said temperature-lowering circulation is higher than that of said balancing circulation.

4. The method for preparing organic fertilizer according to claim 3, characterized in that, Said circulation mode uses a circulation pump as power, said variable-frequency operation mode is a three-stage variable-frequency operation mode, the frequency of said circulation pump can be adjusted in three gears, the shift thresholds T3 and T4 are set according to the type of organic fertilizer, and T3<T4; When T2<ΔT≤T3, said circulation pump operates at 30% to 50% of the rated frequency; When T3<ΔT≤T4, said circulation pump operates at 60% to 80% of the rated frequency; When ΔT>T4, said circulation pump operates at 100% of the rated frequency; When Tw>T1, start said temperature-lowering circulation, and said circulation pump operates at 100% of the rated frequency.

5. The method for preparing organic fertilizer according to claim 2, characterized in that, Said pile core heat exchange adopts the mode of presetting heat exchange pipelines in the pile core, and said heat exchange pipelines are spiral hollow coils.

6. The method for preparing organic fertilizer according to claim 5, characterized in that, Said external temperature control adopts the mode of a water bath temperature control single tube, and said single tube is a water bath heat exchange tube for heating and cooling said heat-carrying medium; The external heat release adopts the method of pre-setting bottom heat release branches and side wall heat release branches in the reactor body. The bottom heat release branch is a comb-shaped pipe located at the bottom of the reactor body, and the side wall heat release branch is a pipe arranged back and forth along the side wall of the reactor body. The single pipe, the bottom heat release branch, the side wall heat release branch, the heat exchange pipeline, and the circulation pump are connected in sequence to form a loop.

7. The method for preparing organic fertilizer according to claim 5, characterized in that, The circulating migration adopts a water bath temperature-controlled dual-pipe method. The dual-pipe consists of two parallel water bath heat exchange pipes used to directly discharge the heat of the heat transfer medium to the outside of the reactor body, and their two ends are respectively connected to the heat exchange pipeline and the circulating pump to form a loop.

8. The method for preparing organic fertilizer according to claim 1, characterized in that, The heat transfer medium is water.

9. The method for preparing organic fertilizer according to claim 1, characterized in that, The pretreatment includes dehydration, crushing, impurity removal and screening, and adjustment of the carbon-nitrogen ratio.

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