Method for simultaneously simulating multiple aerobic composting processes

Abstract

The invention discloses a method for simultaneously simulating multiple aerobic composting processes, and relates to the technical field of resources and environments. Comprising the steps that cobblestones are added into a supporting plate of a composting reactor, a mixed material to be experimented is put into a reaction tank and heated through a heat tracing band, and the reaction tank is located on the supporting plate; covering a nano semi-permeable membrane, sealing by using a flange cover plate, and inserting a temperature probe and an oxygen content probe; covering a gas collection film, and conveying aeration gas into the gas absorption bottle through a pipeline so as to measure the concentrations of CO2, NH3, N2O and H2S in the gas; in the reaction process, the stirrer is used for stirring, the perforated aeration pipe below the supporting plate is used for aeration, the perforated aeration pipe is connected with the oxygen supply pump, and the PLC automatic control system is started for monitoring and control. In one reaction system, comparison, selection and verification of various mainstream aerobic composting processes can be completed, so that the experimental period is greatly shortened. In addition, by adopting the nano semipermeable membrane, the membrane type composting process can be effectively simulated, and the emission of odor is remarkably reduced.

Description

Technical Field

[0001] The invention relates to the technical field of resources and environment, and in particular to a method for simultaneously simulating multiple aerobic composting processes. Background Art

[0002] Aerobic composting technology has been widely used in the treatment and fertilizer production of agricultural solid organic waste. The mainstream processes currently used in engineering applications include static composting, trough composting, and reactor (also known as bin composting) composting. During the feasibility study stage or operation of an actual project, when additional raw materials need to be processed, a small-scale simulated composting experiment is usually required to determine the optimal raw material ratio and process parameters.

[0003] There have been relevant reports on the reaction systems of miniaturized devices simulating aerobic composting processes, among which the most common ones include box composting, vertical or horizontal column reactor composting, etc. Some of these devices use water bath heating, and some are also equipped with stirring devices. However, through field research and review of relevant literature, it is found that the currently used simulated composting devices have the following defects: First, it is impossible to use a single reactor to simultaneously simulate and compare multiple composting processes, such as static composting, membrane composting, tossing composting or reactor composting, which leads to a long experimental cycle; second, the differences in reaction systems brought about by different composting devices may lead to errors in the comparison results, thereby affecting the scientificity and accuracy of the simulation; third, it is impossible to accurately study the interactive effects of environmental parameters such as stirring intensity and cycle, composting temperature, oxygen content, etc. on the composting process; fourth, the spontaneous heat of the device is less than the heat dissipation, making it impossible to fully simulate the composting process in actual engineering. Summary of the invention

[0004] The object of the present invention is to provide a method for simulating multiple aerobic composting processes simultaneously, which can simulate multiple mainstream aerobic composting processes simultaneously, complete the interactive verification of multiple process parameters, improve work efficiency and accuracy, and reduce verification costs.

[0005] To achieve the above-mentioned purpose, the technical solution of the present application is: a method for simulating multiple aerobic composting processes at the same time, comprising: adding pebbles to the support plate of the composting reactor, putting the mixed material to be tested into the reaction tank and heating it through the heating belt, wherein the reaction tank is located on the support plate; then covering the nano semipermeable membrane and sealing it with a flange cover, inserting a temperature probe and an oxygen content probe; covering the gas collecting membrane, and transporting the aeration gas to the gas absorption bottle through a pipeline for measuring CO in the gas. 2 NH 3 、N 2 O, H 2 S concentration;

[0006] During the reaction process, stirring is performed by a stirrer, and aeration is performed by a perforated aeration pipe under the support plate. The perforated aeration pipe is connected to an oxygen supply pump, and a PLC automatic control system is turned on for monitoring and control.

[0007] As a preferred solution of the present invention, the nano semipermeable membrane is a three-layer composite structure, wherein the middle layer is e-PTFE material, the outer layer is hydrophobic PET material, and the inner layer is hydrophilic PET material.

[0008] As a preferred solution of the present invention, regarding the oxygen content in the PLC automatic control system: Logic I, controlling the running and stopping time of the oxygen supply pump by a preset PLC program; Logic II, controlling the start and stop of the oxygen supply pump according to the oxygen content probe data.

[0009] As a preferred solution of the present invention, regarding the temperature in the PLC automatic control system: Logic I, preset the PLC program according to the experimental requirements to control the compost heating time; Logic II, control the compost temperature according to the actual compost temperature rising process; Logic III, when the compost body temperature is greater than 55-70°C, start the oxygen supply pump, and when the compost body temperature is less than 55-70°C, stop the oxygen supply pump;

[0010] As a preferred solution of the present invention, in the PLC automatic control system, regarding stirring, the stirring operation and stop time are controlled by a preset PLC program.

[0011] As a preferred solution of the present invention, the diameter of the aeration holes on the support plate is 3-5 mm, and the gas flow rate is controlled by a rotor flowmeter at 0.02-0.2 m 3 / m 3 ·min.

[0012] As a preferred embodiment of the present invention, the composting reactor has a height-to-diameter ratio of 1:3-2:3 to simulate engineering oxygen mass transfer conditions; an agitator is provided for intermittent stirring to simulate the compost turning process; and a heating belt is wrapped around the outside of the composting reactor to simulate actual compost temperature changes.

[0013] As a preferred solution of the present invention, the composting reactor is externally insulated with a heat-insulating material, and the heat conductivity of the heat-insulating material is between 0.01-0.05 W / m·K.

[0014] As a preferred solution of the present invention, the paving thickness of the pebbles is 3-5% of the height of the composting reactor, the particle size of the bottom layer is 12-15 mm, and the particle size of the upper layer is 5-8 mm.

[0015] As a preferred solution of the present invention, the gas absorption bottle is filled with 0.005-0.02 mol / L sulfuric acid absorption liquid.

[0016] By adopting the above technical solution, the present invention can achieve the following technical effects: in one reaction system, it can complete the comparison and verification of multiple mainstream aerobic composting processes, thereby greatly shortening the experimental period. In addition, the use of nano semipermeable membrane can effectively simulate the membrane composting process and significantly reduce the emission of odor. All components are fixed with bolts, so that users can disassemble and assemble them according to different needs.

[0017] The logic setting of the PLC automatic control system is clear and can complete the interactive verification of the main process parameters of composting. The aperture and flow rate of the aeration system are scientifically calculated to ensure that the oxygen supply requirements can be met under different process conditions. At the same time, the particle size of the paved pebbles has also been verified to ensure the smooth passage of gas and avoid blockage of composting materials. In addition, the use of sulfuric acid absorption liquid with a concentration of 0.005-0.02mol / L can effectively absorb the gases generated in various composting processes for subsequent analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 It is a side view of a device for simulating multiple aerobic composting processes simultaneously;

[0020] Figure 2 It is a top view of the AA surface of a device that simulates multiple aerobic composting processes at the same time;

[0021] Figure 3 It is a BB plane view of a device for simulating multiple aerobic composting processes at the same time;

[0022] Figure 4 It is a top view of the CC surface of a device that simulates multiple aerobic composting processes at the same time;

[0023] Figure 5 It is a temperature variation diagram of the composting body that simulates the implementation of multiple aerobic composting processes at the same time;

[0024] Figure 6 This is a graph showing the change in moisture content of the compost pile during the simultaneous simulation of multiple aerobic composting processes.

[0025] Figure 7 This is a Kjeldahl nitrogen change diagram for a simultaneous simulation of multiple aerobic composting process implementations.

[0026] Explanation of the serial numbers in the figure: 1. Oxygen supply pump, 2. Rotor flowmeter, 3. Oxygen content probe, 4. Temperature probe, 5. Flange cover, 6. Pebbles, 7. Composting reactor, 8. Agitator, 9. Gas collecting membrane, 10. Nano semipermeable membrane, 11. Heating belt, 12. Perforated aeration tube, 13. Gas absorption bottle, 14. Aeration hole. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] Example 1: A composting reactor with a height-to-diameter ratio of 1:3 and a total height of 80 cm was selected. Three layers of rubber-plastic board with a thermal conductivity of 0.03 W / m·K were selected to insulate the composting reactor, and a support plate with an aeration hole diameter of 3 mm was installed. On the support plate, 3 cm pebbles with a diameter of 12 mm were laid on the bottom layer, and 1 cm pebbles with a diameter of 5 mm were laid on the upper layer.

[0029] Reed straw and sludge are used as the main raw materials, and 5% and 10% biochar are used as auxiliary materials. After mixing, they are put into the reaction tank, covered with a nano-semipermeable membrane with e-PTFE material as the middle layer, and the temperature probe and oxygen content probe are inserted; covered with a sealed bag. The stirring start and stop time is set to 15 / 45min; the operation and stop time of the oxygen supply pump using logic I is set to 5 / 25min to control the oxygen content; a combination of logic II and logic III is used to control the compost temperature according to the actual temperature increase process of the compost. When the pile temperature is greater than 50°C, the oxygen supply pump is turned on, and when the pile temperature is less than 60°C, the oxygen supply pump is stopped. The gas flow rate is controlled at 0.05m by a rotor flowmeter 3 / m 3 ·min.

[0030] Cover the gas collecting membrane, connect the gas absorption bottle, and prepare 0.01mol / L sulfuric acid absorption liquid to absorb the CO generated during the composting process. 2 NH 3 、N 2 O, H 2 S gas.

[0031] Turn on the PLC automatic control system and start the experiment.

[0032] Some experimental data are selected for illustration. Figure 5As shown in the figure, the initial temperature of the compost material is about 22°C. After the material is added, the heating belt is turned on to rapidly increase the temperature of the pile body, and it is controlled and maintained at about 55°C by the oxygen supply pump. In the blank experiment, the control temperature is set to 65°C around the 6th day, and the temperature of the pile body rises significantly, reaching a maximum of about 58°C around the 8th day, and gradually drops to 55°C on the 13th day; the temperature of the 5% biochar addition group starts to rise from about the 4th day, reaching a maximum of about 62°C and then begins to decline, and drops to 55°C around the 12th day; the temperature of the 10% biochar addition group starts to rise after the addition, reaching a maximum of 64°C and then begins to decline, and drops to 55°C around the 11th day. The whole cycle system operates well and can reflect the temperature changes of the pile body similarly to the theory; compared with the traditional 50-60 day experimental cycle, the efficiency is significantly improved.

[0033] like Figure 6 As shown, the initial moisture content of the controlled compost was about 70%, and the moisture content after adding biochar was 67.8% and 66.89%, respectively. As the composting progressed, the temperature of the pile gradually increased, and water vapor overflowed from the nano-semipermeable membrane. The moisture content under the condition of adding biochar decreased about 10% faster than the blank experiment, and the 10% addition was also faster than 5%. It reached below 30% in about 32 days, which was in line with national standards and experimental expectations, and the system accuracy was good.

[0034] like Figure 7 As shown in the figure, under the action of nano-semipermeable membrane, the overall nitrogen loss of composting is significantly reduced compared with traditional methods. After the composting is completed, the nitrogen loss of the blank experiment is 22.5%, the loss of 5% biochar addition is 8.5%, and the loss of 10% biochar addition is 5.3%. The Kjeldahl nitrogen loss between different groups is obvious, which is in line with the experimental expectations, and the system has good scientific verification.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for simulating multiple aerobic composting processes simultaneously, characterized in that: include: Pebbles are added to the support plate of the composting reactor, and the mixed materials to be tested are put into the reaction tank and heated by the heating belt, and the reaction tank is located on the support plate; then the nano semi-permeable membrane is covered and sealed with a flange cover, and a temperature probe and an oxygen content probe are inserted; the gas collecting membrane is covered, and the aeration gas is transported to the gas absorption bottle through the pipeline for measuring the concentration of CO2, NH3, N2O, and H2S in the gas; During the reaction process, stirring is performed by a stirrer, and aeration is performed by a perforated aeration pipe under the support plate. The perforated aeration pipe is connected to an oxygen supply pump, and a PLC automatic control system is turned on for monitoring and control.

2. A method for simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: The nano semipermeable membrane is a three-layer composite structure, wherein the middle layer is e-PTFE material, the outer layer is hydrophobic PET material, and the inner layer is hydrophilic PET material.

3. The method for simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: Regarding oxygen content in the PLC automatic control system: Logic I, controls the running and stopping time of the oxygen supply pump through the preset PLC program; Logic II, controls the start and stop of the oxygen supply pump according to the oxygen content probe data.

4. The method of simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: Regarding temperature in the PLC automatic control system: Logic I, preset the PLC program to control the compost heating time according to the experimental requirements; Logic II, controls the compost temperature according to the actual temperature rise process of the compost; Logic III, when the compost temperature is greater than 55-70℃, starts the oxygen supply pump, and when the compost temperature is less than 55-70℃, stops the oxygen supply pump.

5. The method of simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: Regarding stirring in the PLC automatic control system, the stirring operation and stop time are controlled by the preset PLC program.

6. The method for simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: The diameter of the aeration holes on the support plate is 3-5 mm, and the gas flow rate is controlled at 0.02-0.2 m / s by a rotor flow meter. 3 / m 3 ·min.

7. The method for simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: The composting reactor has a height-to-diameter ratio of 1:3-2:3 to simulate engineering oxygen mass transfer conditions; is equipped with an agitator for intermittent stirring to simulate the compost turning process; and is wrapped with a heating belt outside the composting reactor to simulate actual compost temperature changes.

8. The method for simulating multiple aerobic composting processes simultaneously according to claim 7, characterized in that: The outside of the composting reactor is insulated by a heat-insulating material, and the heat-insulating material has a thermal conductivity between 0.01 and 0.05 W / m·K.

9. The method for simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: The paving thickness of the pebbles is 3-5% of the height of the composting reactor, the particle size of the bottom layer is 12-15 mm, and the particle size of the upper layer is 5-8 mm.

10. The method for simulating multiple aerobic composting processes simultaneously according to claim 1, characterized in that: The gas absorption bottle is filled with 0.005-0.02 mol / L sulfuric acid absorption liquid.

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