Biogas energy multi-stage supply and digital energy management method and system

Abstract

The present invention relates to the field of energy management, and in particular to a multi-stage cascade supply and digital energy management method and system for biogas energy. The method performs hierarchical processing on biogas through a multi-dimensional parameter hierarchical decision tree, including a methane concentration diversion layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value assessment layer. Based on steam parameters and waste heat temperature parameters, the temperature difference is calculated and a temperature matching relationship is formed. According to this relationship and the decision tree processing results, the energy utilization path of the biogas is determined, and it is converted into electrical energy, thermal energy, cold energy, steam energy, high-quality suction air, and low-quality suction air to form a multi-energy flow system. The system energy flow data is processed and summarized in real time, compared with the energy demand, and the results are uploaded to a cloud platform for management, thereby realizing digital management of multi-stage cascade supply of biogas energy. This method improves energy utilization efficiency, utilizes biogas in a refined and graded manner, selects the best utilization path according to its quality characteristics, and maximizes the energy value of biogas of different qualities.

Description

Technical Field

[0001] The present invention relates to the field of energy management, and in particular to a method and system for multi-stage combined supply and digital energy management of biogas energy, which is suitable for efficient cascade utilization and intelligent management of biogas energy in the papermaking industry. Background Art

[0002] The papermaking industry is one of the most energy-intensive sectors, generating significant amounts of biogas during pulping, fiber production, and papermaking. Traditional biogas utilization relies primarily on simple combustion for power generation or heating, failing to fully realize its potential and resulting in low energy efficiency.

[0003] Existing biogas utilization technologies have the following problems: first, there is a lack of refined analysis and graded utilization of biogas quality, making it impossible to carry out targeted treatment according to the different characteristics of biogas; second, the mismatch between biogas energy and the energy requirements of the papermaking process leads to the waste of high-grade energy by using low-grade energy; third, there is a lack of precise recovery and reuse mechanisms for waste heat resources, resulting in energy waste; finally, there is a lack of digital and intelligent energy management systems, making it impossible to achieve real-time monitoring and optimized allocation of energy flows.

[0004] Therefore, there is an urgent need for a technical solution that can carry out fine-grained graded utilization of biogas, realize multi-level energy co-supply, and have digital management capabilities to improve the energy utilization efficiency and economic benefits of the papermaking industry. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-stage combined supply and digital energy management method and system for biogas energy, to realize the refined hierarchical utilization of biogas through a multi-dimensional parameter hierarchical decision tree, to realize the precise matching of energy through a temperature difference-driven energy distribution mechanism, to realize the economic optimization of energy utilization through dynamic heat price calculation and economic-driven waste heat distribution, to realize the precise control of energy flow through precise control execution and valve network collaborative system, and to realize the intelligentization of energy management through a closed-loop optimization system integrated in a cloud platform, thereby improving the utilization efficiency and economic benefits of biogas energy in the papermaking industry.

[0006] The present invention proposes a multi-stage biogas energy supply and digital energy management method, including:

[0007] Obtain biogas parameters, steam parameters and waste heat temperature parameters generated in the pulping, fiber making and paper making processes of papermaking enterprises;

[0008] Based on the biogas parameters, the biogas is graded using a multi-dimensional parameter hierarchical decision tree, wherein the multi-dimensional parameter hierarchical decision tree includes a methane concentration diversion layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value assessment layer;

[0009] calculating a first temperature difference and a second temperature difference according to the steam parameter and the waste heat temperature parameter, and forming a temperature matching relationship based on the first temperature difference and the second temperature difference;

[0010] Based on the temperature matching relationship and the hierarchical processing results of the multi-dimensional parameter hierarchical decision tree, an energy utilization path of the biogas is determined, and the biogas is converted into electrical energy, heat energy, cold energy, steam energy, high-quality suction air and low-quality suction air according to the energy utilization path to form a multi-energy flow system;

[0011] The energy flow data in the multi-energy flow system is processed and summarized in real time, compared with the energy demand, and the comparison results are uploaded to the cloud platform for management, thereby realizing the digital management of multi-level cascade biogas energy.

[0012] Preferably, the specific decision-making process of the multi-dimensional parameter hierarchical decision tree includes:

[0013] In the methane concentration diversion layer, the methane ratio in the biogas is obtained. When the methane ratio is greater than a preset threshold, the biogas enters a high-quality biogas treatment path. When the methane ratio is less than a preset threshold, the biogas enters a low-quality biogas treatment path. The preset threshold is 80%.

[0014] In the volume analysis layer, the biogas volume is obtained. When the biogas volume is greater than a preset volume threshold, the biogas is directly used as combustion air. When the biogas volume is less than the preset volume threshold, the temperature difference comparison layer is entered, where the preset volume threshold is 100m³ / h.

[0015] In the temperature difference comparison layer, the biogas temperature is obtained and compared with the first temperature difference and the second temperature difference. When the biogas temperature is less than the first temperature difference, the biogas is added as combustion air. When the biogas temperature is greater than the first temperature difference and less than the second temperature difference, the biogas is mixed with steam and then burned. When the biogas temperature is greater than the second temperature difference, the biogas is directly burned and utilized through the high-efficiency combustion channel.

[0016] In the calorific value assessment layer, when the difference between the biogas temperature and the second temperature difference is greater than a preset temperature difference threshold, the low calorific value and the low combustion calorific value of the biogas are obtained, and the final treatment method of the biogas is determined based on the low calorific value and the low combustion calorific value, where the preset temperature difference threshold is 10°C.

[0017] Preferably, the specific processing process of the calorific value assessment layer includes:

[0018] Obtain low calorific value and low combustion calorific value of biogas;

[0019] When the low calorific value is less than the first calorific value threshold and the low combustion calorific value is less than the second calorific value threshold, the biogas is added as combustion air into the biomass combustion air channel;

[0020] When the low calorific value is greater than the first calorific value threshold and the low combustion calorific value is less than the second calorific value threshold, the biogas is mixed with steam and burned in the combustion calorific value channel, and then the burned gas is supplied to the steam channel of the biomass slurry tower through the superheated steam supply channel;

[0021] When the low calorific value is less than the first calorific value threshold and the low combustion calorific value is greater than the second calorific value threshold, the biogas is mixed with steam and burned in the combustion calorific value channel, and then the burned gas is supplied to the steam channel of the biomass slurry tower through the superheated steam supply channel;

[0022] When the low calorific value is greater than the first calorific value threshold and the low combustion calorific value is greater than the second calorific value threshold, the biogas is added as combustion air into the biomass combustion air channel;

[0023] Among them, the first calorific value threshold is 21000kj / m³, and the second calorific value threshold is 24000kj / m³.

[0024] Preferably, the calculation process of the first temperature difference and the second temperature difference includes:

[0025] Obtaining a temperature required for papermaking and a waste heat temperature before waste heat utilization in a papermaking workshop, matching the temperature required for papermaking with the waste heat temperature before waste heat utilization to obtain the first temperature difference;

[0026] Obtaining a temperature required for papermaking and a waste heat temperature after waste heat recovery in a papermaking workshop, matching the temperature required for papermaking with the waste heat temperature after waste heat recovery to obtain a second temperature difference;

[0027] Among them, when the temperature difference is greater than zero, it means that the energy is insufficient and energy needs to be replenished; when the temperature difference is less than zero, it means that the energy is excessive and energy needs to be recycled.

[0028] Preferably, the process of converting biogas into a multi-energy flow system includes:

[0029] Obtaining steam temperature and steam pressure, and when the steam pressure is greater than a preset pressure threshold and the steam temperature is greater than a preset temperature threshold, adding steam to the steam pipeline of the biomass slurry tower; when the steam pressure is less than the preset pressure threshold or the steam temperature is less than the preset temperature threshold, stopping adding steam to the steam pipeline;

[0030] The preset pressure threshold is 3 bar, and the preset temperature threshold is 135°C.

[0031] The high-quality thermal energy of 0.8MPa drives the steam turbine to generate electricity with a power generation efficiency of 55%, generating 0.12MPa of thermal energy to supply steam;

[0032] The medium-quality heat energy of 0.3MPa is used for chemicals in pulping process and pulp dilution in papermaking process;

[0033] Through low-quality thermal energy of 50-70℃, a low-pressure organic Rankine cycle is adopted to generate low-temperature hot water driven by steam thermal energy in the form of a heat pump for use in the fiberboard pulping process.

[0034] As a preferred method, the energy economy evaluation and allocation process based on the multi-energy flow system includes:

[0035] The heat price of co-steam and purchased steam is determined based on the gas state parameters and waste heat temperature in the gas production pool and the conversion relationship between waste heat and electricity price;

[0036] Determine the heat price conversion ratio based on the ratio of the calorific value of the biogas in the gas production pool to the calorific value of the co-steam;

[0037] Determine the combined supply ratio of co-supplied steam and purchased steam based on the ratio of the co-supplied steam calorific value to the steam calorific value required for waste heat co-supplied steam;

[0038] The product of the combined power ratio and the heat price is used to obtain a gas purchase price and a gas sales price;

[0039] When the purchase price of gas is higher than the sales price, the waste heat is sold;

[0040] When the gas purchase price is lower than the sales price, the waste heat is used to prepare steam and supplied through the heat network;

[0041] When the gas purchase price is equal to the sales price, the waste heat is used to prepare steam and transported through the steam pipeline.

[0042] Preferably, the electrical energy, cold energy, heat energy, steam energy, high-quality suction air and low-quality suction air generated in the multi-energy flow system are sequentially transmitted to the cold energy use and heat energy use demand side of the papermaking equipment;

[0043] A multi-energy connector is provided in the multi-energy cascade supply to connect the output end and the input end of the multi-energy cascade supply to facilitate the input and output of the multi-energy flow;

[0044] The multi-energy flow system includes dividing the energy flow into steam energy flow, pulping energy flow, pulping process energy flow, papermaking process energy flow, and fiber process energy flow in sequence. The steam energy flow drives the steam turbine generator by thermal energy. The efficiency of steam turbine power generation is 55%, and the steam thermal energy pressure after passing through the steam turbine is 0.12MPa; the pulping energy flow is sequentially processed by steam energy flow and chemical energy flow input; the pulping process energy flow is used to process the pulping link; the papermaking process energy flow is used to process the papermaking link; and the fiber process energy flow is used to process the fiber production link.

[0045] Preferably, the biogas parameters include biogas volume and methane ratio in the biogas, and the steam parameters include calorific value, mass flow rate, steam temperature and steam pressure;

[0046] The raw materials of papermaking enterprises are processed through three processes: pulping, fiber making and paper making to produce biogas, and the CH4 content in the biogas is between 45-50%.

[0047] The monitoring range of the steam parameters includes: temperature monitoring range of 0-300°C, with an accuracy of ±1°C; pressure monitoring range of 0-5MPa, with an accuracy of ±0.01MPa; flow monitoring adopts ultrasonic flowmeter with an accuracy of ±0.5%.

[0048] Preferably, the energy flow conversion relationship of the multi-energy flow system includes:

[0049] In the papermaking process, the low-grade heat energy and steam heat energy with an evaporation pressure of 0.3MPa in the pulping process, the high-temperature steam with an evaporation pressure of 0.8MPa in the papermaking process and the high-temperature steam driving the steam turbine generator, the steam heat energy after the steam turbine, the output steam heat energy pressure is 0.12MPa;

[0050] In the pulping process, the high-quality heat energy of the fiber process, the high-temperature steam of the pulping process and the high-temperature steam driving the steam turbine generator, the steam heat energy after the steam turbine, the output steam heat energy pressure is 0.12MPa;

[0051] In the fiber process, the high-quality heat energy and evaporation pressure of the pulping process are 0.8MPa high-temperature steam and high-temperature steam drive the turbine generator. The steam heat energy after the steam turbine has an output steam heat energy pressure of 0.12MPa;

[0052] In the multi-energy flow system, valves are provided between the biomass slurry tower, gas production pool, heat storage buffer tank, steam pipeline of the biomass slurry tower, steam heating network of the biomass slurry tower and the steam co-supply heating network, and the valves are controlled by a PLC controller.

[0053] Biogas energy multi-level cogeneration and digital energy management system, including:

[0054] Distributed sensor network, used to obtain biogas parameters, steam parameters and waste heat temperature parameters generated in the pulping, fiber making and paper making processes of papermaking enterprises;

[0055] a multidimensional parameter decision processing unit, configured to perform hierarchical processing on the biogas based on the biogas parameters through a multidimensional parameter hierarchical decision tree, wherein the multidimensional parameter hierarchical decision tree includes a methane concentration diversion layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value assessment layer;

[0056] a temperature matching calculation unit, configured to calculate a first temperature difference and a second temperature difference according to the steam parameter and the waste heat temperature parameter, and form a temperature matching relationship based on the first temperature difference and the second temperature difference;

[0057] an energy path determination unit, configured to determine an energy utilization path of the biogas based on the temperature matching relationship and the hierarchical processing result of the multi-dimensional parameter hierarchical decision tree, and convert the biogas into electrical energy, heat energy, cold energy, steam energy, high-quality suction air, and low-quality suction air according to the energy utilization path, thereby forming a multi-energy flow system;

[0058] A multi-energy cascade supplier, used to transmit the energy flow in the multi-energy flow system, consisting of a plurality of multi-energy cascade suppliers, with cold energy use and heat energy use provided at the output end of the multi-energy cascade supplier, and cold energy input, heat energy input and steam provided at the input end of the multi-energy cascade supplier;

[0059] A multi-stage valve network, including multiple valves arranged between the biomass slurry tower, the gas production pool, and the heat storage buffer tank, wherein the valves are controlled by a PLC controller;

[0060] The digital management unit is used to process and summarize the energy flow data in the multi-energy flow system in real time, compare it with the energy demand, and upload the comparison results to the cloud platform for management, so as to realize the digital management of multi-level cascade biogas energy.

[0061] The present invention has the following beneficial effects:

[0062] 1. Improve energy utilization efficiency: Through a multi-dimensional parameter hierarchical decision tree, biogas is refined and graded for utilization, and the optimal utilization path is selected according to the quality characteristics of biogas, maximizing the energy value of biogas of different qualities and improving energy utilization efficiency by 20-30%.

[0063] 2. Achieve precise matching of energy quality and demand: Through the energy distribution mechanism driven by temperature difference, accurately match energy quality and usage demand, avoid the waste of high-quality energy with low-quality use, and improve the rationality of energy utilization.

[0064] 3. Optimize energy economy: Through dynamic heat price calculation and economic-driven waste heat allocation mechanism, technical optimization and economic optimization are organically combined to achieve comprehensive optimization of energy utilization and improve economic benefits by 15-25%.

[0065] 4. Improve system control accuracy: Through precise valve network coordinated control, accurate regulation of energy flow is achieved, ensuring stable and reliable system operation, and shortening the response time to less than 2 seconds.

[0066] 5. Realize intelligent energy management: Through the closed-loop optimization system integrated into the cloud platform, digital and intelligent energy management is achieved. The system has self-optimization capabilities, reduces manual intervention, and improves management efficiency by 35-45%. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is the overall architecture diagram of the multi-stage biogas energy supply and digital energy management system of the present invention;

[0068] Figure 2 It is a schematic diagram of the structure of the multi-dimensional parameter hierarchical decision tree of the present invention;

[0069] Figure 3 This is a workflow diagram of the temperature difference calculation and energy matching module of the present invention;

[0070] Figure 4 It is the energy conversion relationship diagram of the multi-energy flow system of the present invention;

[0071] Figure 5 It is a data flow diagram of the digital management unit of the present invention. DETAILED DESCRIPTION

[0072] Please refer to the attached Figure 1-5 The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0073] like Figure 1 As shown, the present invention provides a method and system for multi-stage biogas energy cascade supply and digital energy management. The system includes a distributed sensor network 1, a multi-dimensional parameter decision processing unit 2, a temperature matching calculation unit 3, an energy path determination unit 4, a multi-energy cascade supply device 5, a multi-stage valve network 6, and a digital management unit 7. This system is applied in papermaking enterprises to efficiently utilize and intelligently manage biogas generated in the pulping, fiber making, and papermaking processes.

[0074] The multi-stage biogas energy supply and digital energy management method provided by the present invention includes the following steps:

[0075] First, a distributed sensor network 1 is used to obtain biogas parameters, steam parameters, and waste heat temperature parameters generated during the pulping, fiber production, and papermaking processes of a papermaking enterprise. Biogas parameters include biogas volume and the proportion of methane in the biogas, while steam parameters include calorific value, mass flow rate, steam temperature, and steam pressure. In one specific embodiment of the present invention, the distributed sensor network 1 includes a gas production pool monitoring subsystem, a steam parameter monitoring subsystem, and a waste heat temperature monitoring subsystem. The gas production pool monitoring subsystem is installed in the main and auxiliary tanks of the gas production pool and is equipped with methane, hydrogen, carbon dioxide, and oxygen concentration meters. The data acquisition frequency is 30 seconds per data acquisition, with a data acquisition accuracy of ±0.5% for methane concentration and ±1.0% for gas flow. The steam parameter monitoring subsystem is equipped with thermometers, pressure gauges, and flowmeters at key pipeline nodes. The temperature monitoring range is 0-300°C with an accuracy of ±1°C, the pressure monitoring range is 0-5 MPa with an accuracy of ±0.01 MPa, and the flow monitoring uses an ultrasonic flowmeter with an accuracy of ±0.5%. The waste heat temperature monitoring subsystem sets up a temperature sensor array in the papermaking workshop to monitor the temperature changes before and after the waste heat is utilized.

[0076] Secondly, the multi-dimensional parameter decision processing unit 2 performs hierarchical processing on the biogas based on the acquired biogas parameters through a multi-dimensional parameter hierarchical decision tree. Figure 2 As shown in the figure, the multi-dimensional parameter hierarchical decision tree includes a methane concentration classification layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value assessment layer. The methane concentration classification layer performs preliminary classification based on the methane content of the biogas. The volume analysis layer further subdivides the biogas based on its volume. The temperature difference comparison layer selects the biogas treatment path based on temperature matching relationships. The calorific value assessment layer determines the final treatment method for the biogas under specific conditions.

[0077] Then, the temperature matching calculation unit 3 calculates the first temperature difference and the second temperature difference according to the steam parameters and the waste heat temperature parameters, and forms a temperature matching relationship based on the two temperature differences. Figure 3 As shown, the first temperature difference reflects the difference between the required papermaking temperature and the temperature before waste heat utilization, while the second temperature difference reflects the difference between the required papermaking temperature and the temperature after waste heat recovery. These two temperature differences provide key indicators for matching energy demand and supply. In this embodiment of the present invention, when the temperature difference is greater than zero, it indicates energy shortage and requires energy replenishment; when the temperature difference is less than zero, it indicates energy surplus and can be recovered and utilized.

[0078] Next, the energy path determination unit 4 determines the energy utilization path of the biogas based on the temperature matching relationship and the hierarchical processing results of the multi-dimensional parameter hierarchical decision tree, and converts the biogas into electricity, heat, cold, steam, high-quality suction and low-quality suction according to the energy utilization path to form a multi-energy flow system. Figure 4As shown in the figure, the energy conversion relationship in the multi-energy flow system includes the conversion of high-quality thermal energy into electrical energy and medium-quality thermal energy, the use of medium-quality thermal energy for process heating, and the upgrading and utilization of low-quality thermal energy through the organic Rankine cycle.

[0079] Finally, the digital management unit 7 processes and summarizes the energy flow data in the multi-energy flow system in real time, compares it with the energy demand, and uploads the comparison results to the cloud platform for management, thus realizing the digital management of multi-level cascade biogas energy. Figure 5 As shown, the digital management unit 7 realizes closed-loop management of energy data collection, processing, analysis and optimization. Preferably, the digital management unit 7 adopts a layered architecture, including a data storage layer, a data analysis layer and a decision support layer, which can realize digital and intelligent energy management.

[0080] The specific decision-making process of the multi-dimensional parameter hierarchical decision tree in the present invention includes four levels of decision-making steps:

[0081] In the methane concentration diversion layer, the methane content in the biogas is obtained through a methane concentration meter. When the methane content is greater than the preset threshold, it enters the high-quality biogas treatment path. When the methane content is less than the preset threshold, it enters the low-quality biogas treatment path. Preferably, the preset threshold is set to 80%. The selection of this threshold is based on the actual empirical value of biogas utilization efficiency. When the methane content exceeds 80%, the combustion efficiency and calorific value of the biogas are significantly improved, making it suitable for direct use as a high-quality fuel. When the methane content is less than 80%, the combustion efficiency is relatively low, and additional treatment measures are required to improve its utilization value.

[0082] In the volume analysis layer, a flow meter measures biogas volume. When the biogas volume exceeds a preset threshold, it is used directly as combustion air. When the biogas volume falls below the threshold, it enters the temperature difference comparison layer for further analysis. Preferably, the preset volume threshold is set at 100 m³ / h. This threshold is determined based on practical application experience. When biogas production exceeds 100 m³ / h, it is sufficient for use as primary fuel. When production falls below this threshold, more refined allocation, combined with temperature requirements, is required to achieve optimal energy utilization.

[0083] In the temperature difference comparison layer, the biogas temperature is obtained and compared with the first and second temperature differences, forming three processing paths: when the biogas temperature is less than the first temperature difference, the biogas is used as combustion air; when the biogas temperature is greater than the first temperature difference but less than the second temperature difference, the biogas is mixed with steam and then burned; when the biogas temperature is greater than the second temperature difference, the biogas is directly burned through the high-efficiency combustion channel. This temperature difference-based decision-making mechanism achieves precise energy matching and avoids energy waste.

[0084] In the calorific value assessment layer, when the difference between the biogas temperature and the second temperature difference exceeds a preset temperature difference threshold, the biogas's low calorific value and low combustion calorific value are obtained, and the final biogas treatment method is determined based on these two parameters. Preferably, the preset temperature difference threshold is set to 10°C. This threshold is selected based on the efficiency of heat energy transfer and the allowable temperature difference range in actual projects. When the temperature difference exceeds 10°C, the calorific value assessment stage is entered, allowing for more precise determination of energy utilization paths.

[0085] In addition, to ensure the rationality of decision-making, the present invention also sets up a path priority mechanism: the first priority is safety considerations to ensure stable operation of the system; the second priority is energy efficiency, giving priority to paths with high energy utilization efficiency; the third priority is economy, and the path with the best economic benefits is selected when the first two conditions are met.

[0086] The specific processing process of the calorific value assessment layer in the present invention includes four types of biogas treatment methods:

[0087] First, calorific value measurement equipment is used to obtain the biogas's low calorific value and low combustion calorific value. The low calorific value reflects the energy released by the combustible components in the biogas, while the low combustion calorific value reflects the efficiency of heat energy conversion during combustion. These two parameters together determine the energy value of the biogas and its optimal utilization.

[0088] When the low calorific value is less than the first calorific value threshold and the low combustion calorific value is less than the second calorific value threshold, biogas is added as combustion air to the biomass combustion air channel. In this case, the energy value of biogas is low and it is suitable for use as an auxiliary fuel.

[0089] When the low calorific value exceeds the first calorific value threshold and the low combustion calorific value is less than the second calorific value threshold, the biogas is mixed with steam and burned in the combustion calorific value channel. The combusted gas is then supplied to the steam channel of the biomass slurry tower through the superheated steam supply channel. In this case, the biogas has a high energy content but low combustion efficiency. Mixing it with steam can improve its utilization efficiency.

[0090] When the low calorific value is less than the first calorific value threshold and the low combustion calorific value is greater than the second calorific value threshold, the biogas is similarly mixed with steam and burned through the combustion calorific value channel before being transported through the superheated steam supply channel. In this case, although the biogas has a low energy content, its combustion efficiency is high, and mixing it with steam can fully utilize its combustion efficiency advantages.

[0091] When the low calorific value exceeds the first calorific value threshold and the low combustion calorific value exceeds the second calorific value threshold, the biogas is directly burned and utilized through the high-efficiency combustion channel. In this case, the biogas has high energy content and combustion efficiency, making it suitable for direct use as the main fuel.

[0092] Preferably, the first calorific value threshold is set to 21,000 kJ / m³, and the second calorific value threshold is set to 24,000 kJ / m³. These two thresholds are set based on actual experience in biogas energy utilization and engineering application data, and can effectively distinguish between biogas of different qualities and select the best utilization path for them.

[0093] The calculation process of the first temperature difference and the second temperature difference in the present invention includes:

[0094] First, the temperature matching calculation unit 3 obtains the required temperature for papermaking and the waste heat temperature before waste heat utilization in the papermaking workshop. In a specific embodiment of the present invention, the required temperature for papermaking is typically in the range of 135-150°C, depending on the specific paper product type and process requirements. The waste heat temperature before waste heat utilization is typically in the range of 80-120°C, depending on process conditions and equipment status.

[0095] Then, the temperature matching calculation unit 3 matches the temperature required for papermaking with the waste heat temperature before waste heat utilization to calculate a first temperature difference. The calculation formula is:

[0096] ,

[0097] in, is the first temperature difference, in °C; is the temperature required for papermaking, in °C; is the temperature before waste heat utilization, in °C. This formula represents the difference between the temperature required for papermaking and the temperature before waste heat utilization, reflecting the gap between energy demand and initial available energy.

[0098] Next, the temperature matching calculation unit 3 obtains the temperature required for papermaking and the waste heat temperature after waste heat recovery in the papermaking workshop. The waste heat temperature after waste heat recovery is usually in the range of 40-80°C, depending on the efficiency of the recovery equipment and the surrounding environmental conditions.

[0099] Then, the temperature matching calculation unit 3 matches the temperature required for papermaking with the waste heat temperature after waste heat recovery to calculate the second temperature difference. The calculation formula is:

[0100] ,

[0101] in, is the second temperature difference, in °C; is the temperature required for papermaking, in °C; is the temperature after waste heat recovery, in °C. This formula represents the difference between the temperature required for papermaking and the temperature after waste heat recovery, reflecting the gap between energy demand and secondary available energy.

[0102] These two temperature differences provide important indicators for energy matching. When the temperature difference is greater than zero, it indicates energy shortage and requires replenishment; when the temperature difference is less than zero, it indicates energy surplus and can be recycled. This temperature-differential-driven energy allocation mechanism enables precise energy matching and avoids energy waste.

[0103] In one embodiment of the present invention, assuming the required temperature for papermaking is 145°C, the temperature before waste heat utilization is 110°C, and the temperature after waste heat recovery is 60°C, the calculated first temperature difference is 35°C, and the second temperature difference is 85°C. These two temperature differences are used in the decision-making process of the temperature difference comparison layer to guide the rational use of biogas.

[0104] The process of converting biogas into a multi-energy flow system in the present invention comprises the following steps:

[0105] First, the steam temperature and pressure are acquired through the steam parameter monitoring subsystem. In this embodiment of the present invention, a thermometer is used to monitor the steam temperature, with a temperature monitoring range of 0-300°C and an accuracy of ±1°C; a pressure gauge is used to monitor the steam pressure, with a pressure monitoring range of 0-5MPa and an accuracy of ±0.01MPa.

[0106] Then, based on the acquired steam parameters, a determination is made as to whether steam needs to be added to the biomass pulp tower. When the steam pressure exceeds a preset pressure threshold and the steam temperature exceeds a preset temperature threshold, steam is added to the steam pipeline of the biomass pulp tower. When the steam pressure falls below the preset pressure threshold or the steam temperature falls below the preset temperature threshold, steam addition to the steam pipeline is stopped. Preferably, the preset pressure threshold is set to 3 bar, and the preset temperature threshold is set to 135°C. These two thresholds are set based on the actual needs of the papermaking process and the requirements for safe equipment operation, ensuring that the steam provided meets process requirements while ensuring safe and stable system operation.

[0107] Next, the energy path determination unit 4 converts the biogas into various energy forms to form a multi-energy flow system. First, the high-quality thermal energy of 0.8MPa is used to drive the steam turbine to generate electricity, with a power generation efficiency of 55%, generating 0.12MPa of thermal energy to supply steam. High-quality thermal energy mainly comes from the high-temperature steam generated in the papermaking process, with a temperature usually in the range of 180-200°C. The steam turbine converts the thermal energy of the steam into mechanical energy, which in turn drives the generator to generate electricity, achieving efficient energy utilization.

[0108] Second, 0.3 MPa of medium-grade heat is used for chemical processing in the pulping process and pulp dilution in the papermaking process. This medium-grade heat primarily comes from medium-temperature steam generated during the pulping process, typically in the 140-160°C range. This heat provides the medium-temperature heat source required to meet the temperature requirements of specific process steps.

[0109] Finally, using low-quality heat energy at 50-70°C, a low-pressure organic Rankine cycle (ORC) is used to generate low-temperature hot water for fiberboard pulping, using steam heat as a heat pump. This low-quality heat energy primarily comes from low-temperature waste heat generated during the pulping process, and the ORC improves its quality, achieving cascaded energy utilization.

[0110] In the organic Rankine cycle, an organic working fluid (such as R245fa or R134a) suitable for low-temperature heat sources at 50-70°C is used as the working medium. It absorbs low-quality heat energy in the evaporator and evaporates. The vapor drives the expander to perform work. The vapor then releases heat and condenses into a liquid in the condenser, which is then pumped back to the evaporator to complete the cycle. This process converts low-quality heat energy into a more valuable form of energy, improving energy efficiency.

[0111] The energy economy evaluation and allocation process based on the multi-energy flow system in the present invention includes the following steps:

[0112] First, the gas state parameters in the gas production pool are acquired through the gas production pool monitoring subsystem, and the waste heat temperature is acquired through the waste heat temperature monitoring subsystem. In a specific embodiment of the present invention, the gas state parameters include methane content, gas flow rate, temperature, and pressure. The waste heat temperature is acquired with an accuracy of ±1°C using a temperature sensor array installed in the papermaking workshop.

[0113] Then, the digital management unit 7 calculates the heat price of the co-steam and purchased steam based on the conversion relationship between waste heat and electricity price. The heat price calculation takes into account multiple factors, including the calorific value of biogas, the calorific value of steam, the current electricity price and the waste heat temperature. The heat price calculation formula is:

[0114] ,

[0115] in, is the price of cogeneration steam heat, in yuan / ton; is the conversion factor, dimensionless, usually ranging from 0.8 to 0.9; is the calorific value of biogas, in kj / m is the current electricity price, in yuan / kWh; is the calorific value of steam, in kj / kg; is the temperature correction factor, dimensionless, usually in the range of 0.1-0.2; is the waste heat temperature in °C; is the maximum waste heat temperature in °C, usually set to 200 °C. This formula takes into account factors such as energy price, calorific value and temperature to calculate the comprehensive heat price of co-generation steam.

[0116] Next, the digital management unit 7 obtains the market price of steam , in yuan / ton, which is usually the price quoted by local heating companies. Then calculate the heat price ratio , dimensionless, this ratio reflects the economic comparison between self-produced steam and purchased steam.

[0117] Then, the digital management unit 7 determines the heat price conversion ratio based on the ratio of the calorific value of the biogas in the gas production pool to the calorific value of the co-steam. The heat price conversion ratio calculation formula is:

[0118] ,

[0119] in, is the heat price conversion ratio, dimensionless; is the calorific value of biogas, in kj / m³; is the calorific value of the co-steam, expressed in kJ / kg. This ratio represents the energy ratio of a unit of biogas to a unit of co-steam, reflecting the energy conversion efficiency.

[0120] Next, the digital management unit 7 determines the combined supply ratio of the combined steam and the purchased steam based on the ratio of the combined steam calorific value to the steam calorific value required for the waste heat combined supply. The combined supply ratio calculation formula is:

[0121] ,

[0122] in, is the combined power generation ratio, dimensionless; is the calorific value of the co-steam, in kj / kg; The calorific value of the steam required for waste heat cogeneration is expressed in kJ / kg. This ratio represents the energy ratio of the cogeneration steam to the steam required for waste heat cogeneration, reflecting the degree of heat supply and demand matching.

[0123] Then, the product of the combined power ratio and the heat price is used to obtain the gas purchase price and sales price. The formula for calculating the gas purchase price is:

[0124] ,

[0125] in, is the gas purchase price, dimensionless, representing the relative price index of purchasing biogas; is the heat price conversion ratio, dimensionless; is the combined power generation ratio, dimensionless; is the heat price ratio, dimensionless. This calculation result is used to compare with the sales price to determine the most economically efficient energy utilization path.

[0126] Sales Price , dimensionless, represents the relative price index of biogas sales, which is usually market pricing and is affected by many factors, including regional supply and demand, seasonal changes, etc.

[0127] Finally, the digital management unit 7 determines the optimal utilization path of waste heat based on the comparison of gas purchase price and sales price:

[0128] When the purchase price is higher than the sales price, the waste heat is sold. In this case, selling the waste heat is more economical than using it yourself;

[0129] When the purchase price is lower than the sales price, the waste heat is used to prepare steam and supply it through the heat network. In this case, it is more economical to use the waste heat yourself than to sell it;

[0130] When the gas purchase price is equal to the gas sales price, the waste heat is used to generate steam and transport it through the steam pipeline. In this case, the two options are economically equivalent and can be flexibly selected based on actual conditions.

[0131] In a specific embodiment of the present invention, it is assumed that the calorific value of biogas is 20,000 kJ / m³, the calorific value of co-generation steam is 2,500 kJ / kg, the calorific value of waste heat co-generation steam is 2,300 kJ / kg, the current electricity price is 0.6 yuan / kWh, the market price of steam is 200 yuan / ton, the conversion coefficient α is 0.85, the temperature correction coefficient β is 0.15, the waste heat temperature is 90°C, and the maximum waste heat temperature is 200°C. Substitute the above heat price calculation formula into the following formula to calculate:

[0132] Combined steam heat price

[0133] 0.0675)=4.57 yuan / ton;

[0134] Heat price ratio ;

[0135] Heat price conversion ratio ;

[0136] Combined power supply ratio ;

[0137] Gas purchase price ;

[0138] Assuming market selling price , assuming the market price ,because ,Therefore, it is more economically reasonable to choose to sell the waste heat.

[0139] The working process of the energy transmission and multi-energy cascade supply of the multi-energy flow system of the present invention includes:

[0140] First, the electricity, cooling energy, heat energy, steam energy, high-quality suction air, and low-quality suction air energy generated by the multi-energy flow system are sequentially transmitted to the cooling and heat energy demand ends of the papermaking equipment. In this embodiment of the present invention, the multi-energy flow system achieves targeted energy transmission through a specially designed pipeline network and control system, ensuring efficient energy utilization and reducing transmission losses.

[0141] Secondly, a multi-energy connector is provided within the multi-energy cascade supply 5 to connect the output and input terminals of the multi-energy cascade supply, facilitating the input and output of multiple energy flows. The multi-energy connector adopts a standardized design to ensure efficient conversion and transmission between different energy forms, improving system integration and operational stability.

[0142] The multi-energy flow system then sequentially divides energy flows into five components: steam flow, pulping flow, pulping process flow, papermaking process flow, and fiber process flow, forming a complete energy utilization chain. The steam flow uses thermal energy to drive the steam turbine generator, which has a power generation efficiency of 55%. After passing through the turbine, the steam thermal pressure is 0.12 MPa. This steam is then used in downstream processes, achieving cascaded energy utilization.

[0143] The pulping energy flow is sequentially processed through steam and chemical energy inputs to provide the energy required for the pulping process. The pulping process energy flow is used to process the pulping phase, including wood chip cooking, washing, and screening. The papermaking process energy flow is used to process the papermaking phase, including pulp forming, pressing, and drying. The fiber process energy flow is used to process the fiber production phase, including fiber preparation and forming.

[0144] During energy transmission, the system utilizes the principles of "temperature drop drive and pressure difference drive" to ensure efficient energy transfer. Furthermore, through precise control of multi-energy cascade power supplies, targeted energy distribution and cascade utilization are achieved, improving overall energy efficiency.

[0145] The detailed description of biogas parameters and steam parameters in the present invention includes:

[0146] Biogas parameters include biogas volume and methane content. Biogas volume reflects the amount of biogas produced and is a key parameter in determining its utilization. The methane content reflects the quality and energy density of the biogas, directly affecting its calorific value and utilization efficiency. In a specific embodiment of the present invention, biogas volume is measured using a flow meter with an accuracy of ±1.0%, while the methane content is measured using a methane concentration meter with an accuracy of ±0.5%.

[0147] Steam parameters include calorific value, mass flow rate, steam temperature, and steam pressure. Calorific value reflects the energy contained in a unit of steam; mass flow rate reflects the steam supply; and steam temperature and pressure determine steam quality and applicable operating conditions. In this invention, steam calorific value is calculated through heat calculations; mass flow rate is measured using a flowmeter; steam temperature is measured using a thermometer with a range of 0-300°C and an accuracy of ±1°C; and steam pressure is measured using a pressure gauge with a range of 0-5 MPa and an accuracy of ±0.01 MPa.

[0148] Preferably, the papermaking enterprise produces biogas after the raw materials undergo three processes: pulping, fiber making, and papermaking. The CH4 content in the biogas is between 45-50%. This methane content range is determined based on actual production data and reflects the typical characteristics of biogas in the papermaking industry. Compared with biogas produced by other industries (such as livestock biogas, which generally has a CH4 content of 60-70%), the methane content of biogas produced by the papermaking industry is relatively low, but through the technical solution of the present invention, it can still be efficiently utilized.

[0149] The energy flow conversion relationship of the multi-energy flow system in the present invention includes energy conversion in three main process flows:

[0150] In the papermaking process, low-grade heat energy from the pulping process and steam energy with an evaporation pressure of 0.3 MPa, as well as high-temperature steam with an evaporation pressure of 0.8 MPa from the papermaking process, are used to drive steam turbine generators, achieving efficient energy utilization. After passing through the steam turbine, the steam heat energy is output at a pressure of 0.12 MPa and is further used in subsequent processes. This multi-stage utilization model significantly improves the overall efficiency of energy utilization.

[0151] In the pulping process, high-quality heat from the fiber process, high-temperature steam from the pulping process, and high-temperature steam driving the turbine generator also achieve cascade energy utilization. After passing through the turbine, the steam heat energy is output at a pressure of 0.12 MPa and used to meet other process needs. This combined energy utilization reduces energy waste and improves overall system efficiency.

[0152] In the fiber process, the high-quality heat energy and evaporation pressure of 0.8MPa high-temperature steam from the pulping process are used to drive the steam turbine generator, further realizing the comprehensive utilization of energy. The steam heat energy after passing through the steam turbine has an output steam heat energy pressure of 0.12MPa and is put into use.

[0153] Throughout the multi-energy flow system, valves are installed between the biomass slurry tower, gas production tank, thermal storage buffer tank, biomass slurry tower steam pipeline, biomass slurry tower steam heating network, and steam cogeneration heating network, forming a complete control network. All valves are controlled by a PLC controller, enabling centralized control and precise regulation of the system.

[0154] The PLC controller utilizes industrial-grade control equipment with high reliability and real-time performance, enabling real-time monitoring and adjustment of system operating status. In a specific embodiment of the present invention, the PLC controller utilizes a modular design, including a CPU module, power module, input / output module, and communication module. It communicates with various sensors and actuators via Industrial Ethernet, with a 50ms communication cycle, ensuring timely and accurate control.

[0155] The biogas energy multi-stage combined supply and digital energy management system provided by the present invention includes the following units:

[0156] Distributed sensor network 1 is used to collect biogas parameters, steam parameters, and waste heat temperature parameters generated during the pulping, fiber production, and papermaking processes of papermaking enterprises. The distributed sensor network adopts a three-tier architecture: the field layer includes various sensors and data acquisition devices; the network layer includes industrial Ethernet and wireless sensor networks; and the management layer includes data servers and monitoring terminals. This layered architecture improves system reliability and scalability.

[0157] The multi-dimensional parameter decision processing unit 2 is used to hierarchically process biogas based on biogas parameters using a multi-dimensional parameter hierarchical decision tree. This unit utilizes a modular design, comprising a parameter preprocessing module, a decision tree execution module, and a result output module. The decision tree structure is implemented in software, allowing for parameter adjustment and optimization based on actual needs.

[0158] The temperature matching calculation unit 3 is used to calculate the first temperature difference and the second temperature difference based on the steam parameters and the waste heat temperature parameters, and form a temperature matching relationship. The temperature matching calculation unit uses a specialized algorithm to perform temperature difference calculation and matching analysis, providing a key basis for energy allocation.

[0159] Energy Path Determination Unit 4 determines the biogas' energy utilization path based on the temperature matching relationship and the hierarchical processing results of the multi-dimensional parameter hierarchical decision tree, converting the biogas into various energy forms to form a multi-energy flow system. The Energy Path Determination Unit uses an optimization algorithm to achieve optimal energy allocation decisions, ensuring maximum system efficiency.

[0160] The multi-energy cascade supply 5 is used to transmit energy flows within the multi-energy flow system and is composed of multiple multi-energy cascade supplies. Each multi-energy cascade supply has an input and an output. The output is equipped with interfaces for cold energy use and heat energy use, and the input is equipped with interfaces for cold energy input, heat energy input, and steam input. The multi-energy cascade supply adopts a standardized design, which facilitates system integration and expansion.

[0161] The multi-stage valve network 6 includes multiple valves located between the biomass slurry tower, gas production tank, and thermal storage buffer tank. All valves are controlled by a PLC controller, enabling precise control and regulation of the system. The multi-stage valve network utilizes a redundant design, enhancing system reliability and safety.

[0162] The digital management unit 7 processes and aggregates energy flow data from the multi-energy flow system in real time, compares it with energy demand, and uploads the comparison results to the cloud platform for management. The digital management unit utilizes a cloud-edge-end architecture to achieve distributed data processing and centralized management. The cloud platform provides data storage, analysis, and decision support; edge computing nodes implement data preprocessing and real-time response; and terminal devices are responsible for data collection and execution.

[0163] During system implementation, standardized interfaces and communication protocols enable data exchange and collaborative work between various units. The system's modular design facilitates maintenance and upgrades. Furthermore, the system is equipped with security mechanisms, including data encryption, access control, and anomaly detection, to ensure the safety and reliability of system operation.

[0164] In summary, the multi-stage combined supply and digital energy management method and system of biogas energy provided by the present invention realizes the refined hierarchical utilization of biogas through a multi-dimensional parameter hierarchical decision tree, realizes precise matching of energy through an energy distribution mechanism driven by temperature difference, realizes economic optimization of energy utilization through dynamic heat price calculation and economic-driven waste heat distribution, realizes precise control of energy flow through precise control execution and valve network collaborative system, and realizes intelligent energy management through a closed-loop optimization system integrated in a cloud platform, thereby improving the utilization efficiency and economic benefits of biogas energy in the papermaking industry.

[0165] The invention has broad industrial application prospects. It is not only applicable to the papermaking industry, but can also be extended to other industrial fields that produce biogas, such as food processing, brewing, sugar making and other industries, providing a new technical approach for industrial energy conservation and emission reduction.

[0166] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A multi-stage biogas energy supply and digital energy management method, characterized in that: include: Obtain biogas parameters, steam parameters and waste heat temperature parameters generated in the pulping, fiber making and paper making processes of papermaking enterprises; Based on the biogas parameters, the biogas is graded using a multi-dimensional parameter hierarchical decision tree, wherein the multi-dimensional parameter hierarchical decision tree includes a methane concentration diversion layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value assessment layer; calculating a first temperature difference and a second temperature difference according to the steam parameter and the waste heat temperature parameter, and forming a temperature matching relationship based on the first temperature difference and the second temperature difference; Based on the temperature matching relationship and the hierarchical processing results of the multi-dimensional parameter hierarchical decision tree, an energy utilization path of the biogas is determined, and the biogas is converted into electrical energy, heat energy, cold energy, steam energy, high-quality suction air and low-quality suction air according to the energy utilization path to form a multi-energy flow system; The energy flow data in the multi-energy flow system is processed and summarized in real time, compared with the energy demand, and the comparison results are uploaded to the cloud platform for management, thereby realizing the digital management of multi-level cascade biogas energy.

2. The biogas energy multi-stage combined supply and digital energy management method according to claim 1 is characterized in that: The specific decision-making process of the multi-dimensional parameter hierarchical decision tree includes: In the methane concentration diversion layer, the methane ratio in the biogas is obtained. When the methane ratio is greater than a preset threshold, the biogas enters a high-quality biogas treatment path. When the methane ratio is less than a preset threshold, the biogas enters a low-quality biogas treatment path. The preset threshold is 80%. In the volume analysis layer, the biogas volume flow rate is obtained. When the biogas volume flow rate is greater than a preset volume flow rate threshold, the biogas is directly used as combustion air. When the biogas volume flow rate is less than the preset volume flow rate threshold, the temperature difference comparison layer is entered, where the preset volume flow rate threshold is 100 m³ / h. In the temperature difference comparison layer, the biogas temperature is obtained and compared with the first temperature difference and the second temperature difference. When the biogas temperature is less than the first temperature difference, the biogas is added as combustion air. When the biogas temperature is greater than the first temperature difference and less than the second temperature difference, the biogas is mixed with steam and then burned. When the biogas temperature is greater than the second temperature difference, the biogas is directly burned and utilized through the high-efficiency combustion channel. In the calorific value assessment layer, when the difference between the biogas temperature and the second temperature difference is greater than a preset temperature difference threshold, the low calorific value and the low combustion calorific value of the biogas are obtained, and the final treatment method of the biogas is determined based on the low calorific value and the low combustion calorific value, where the preset temperature difference threshold is 10°C.

3. The biogas energy multi-stage combined supply and digital energy management method according to claim 2 is characterized in that: The specific processing process of the calorific value assessment layer includes: Obtain low calorific value and low combustion calorific value of biogas; When the low calorific value is less than the first calorific value threshold and the low combustion calorific value is less than the second calorific value threshold, the biogas is added as combustion air into the biomass combustion air channel; When the low calorific value is greater than the first calorific value threshold and the low combustion calorific value is less than the second calorific value threshold, the biogas is mixed with steam and burned in the combustion calorific value channel, and then the burned gas is supplied to the steam channel of the biomass slurry tower through the superheated steam supply channel; When the low calorific value is less than the first calorific value threshold and the low combustion calorific value is greater than the second calorific value threshold, the biogas is mixed with steam and burned in the combustion calorific value channel, and then the burned gas is supplied to the steam channel of the biomass slurry tower through the superheated steam supply channel; When the low calorific value is greater than the first calorific value threshold and the low combustion calorific value is greater than the second calorific value threshold, the biogas is added as combustion air into the biomass combustion air channel; Among them, the first calorific value threshold is 21000kJ / m³, and the second calorific value threshold is 24000kJ / m³.

4. The biogas energy multi-stage combined supply and digital energy management method according to claim 1 is characterized in that: The calculation process of the first temperature difference and the second temperature difference includes: Obtaining a temperature required for papermaking and a waste heat temperature before waste heat utilization in a papermaking workshop, matching the temperature required for papermaking with the waste heat temperature before waste heat utilization to obtain the first temperature difference; Obtaining a temperature required for papermaking and a waste heat temperature after waste heat recovery in a papermaking workshop, matching the temperature required for papermaking with the waste heat temperature after waste heat recovery to obtain a second temperature difference; Among them, when the temperature difference is greater than zero, it means that the energy is insufficient and energy needs to be replenished; when the temperature difference is less than zero, it means that the energy is excessive and energy needs to be recycled.

5. The biogas energy multi-stage combined supply and digital energy management method according to claim 1 is characterized in that: The process of converting biogas into a multi-energy flow system includes: Obtaining steam temperature and steam pressure, and when the steam pressure is greater than a preset pressure threshold and the steam temperature is greater than a preset temperature threshold, adding steam to the steam pipeline of the biomass slurry tower; when the steam pressure is less than the preset pressure threshold or the steam temperature is less than the preset temperature threshold, stopping adding steam to the steam pipeline; The preset pressure threshold is 3 bar, and the preset temperature threshold is 135°C. The high-quality thermal energy of 0.8MPa drives the steam turbine to generate electricity with a power generation efficiency of 55%, generating 0.12MPa of thermal energy to supply steam; The medium-quality heat energy of 0.3MPa is used for chemicals in pulping process and pulp dilution in papermaking process; Through low-quality thermal energy of 50-70℃, a low-pressure organic Rankine cycle is adopted to generate low-temperature hot water driven by steam thermal energy in the form of a heat pump for use in the fiberboard pulping process.

6. The biogas energy multi-stage combined supply and digital energy management method according to claim 1 is characterized in that: The energy economic evaluation and allocation process based on the multi-energy flow system includes: The heat price of co-steam and purchased steam is determined based on the gas state parameters and waste heat temperature in the gas production pool and the conversion relationship between waste heat and electricity price; Determine the heat price conversion ratio based on the ratio of the calorific value of the biogas in the gas production pool to the calorific value of the co-steam; Determine the combined supply ratio of co-supplied steam and purchased steam based on the ratio of the co-supplied steam calorific value to the steam calorific value required for waste heat co-supplied steam; The product of the combined power ratio and the heat price is used to obtain a gas purchase price and a gas sales price; When the purchase price of gas is higher than the sales price, the waste heat is sold; When the gas purchase price is lower than the sales price, the waste heat is used to prepare steam and supplied through the heat network; When the gas purchase price is equal to the sales price, the waste heat is used to prepare steam and transported through the steam pipeline.

7. The biogas energy multi-stage combined supply and digital energy management method according to claim 1 is characterized in that: The electrical energy, cold energy, heat energy, steam energy, high-quality suction air and low-quality suction air energy generated in the multi-energy flow system are sequentially transmitted to the cold energy and heat energy demand ends of the papermaking equipment; A multi-energy connector is provided in the multi-energy cascade supply to connect the output end and the input end of the multi-energy cascade supply to facilitate the input and output of the multi-energy flow; The multi-energy flow system includes dividing the energy flow into steam energy flow, pulping energy flow, pulping process energy flow, papermaking process energy flow, and fiber process energy flow in sequence. The steam energy flow drives the steam turbine generator by thermal energy. The efficiency of steam turbine power generation is 55%, and the steam thermal energy pressure after passing through the steam turbine is 0.12MPa; the pulping energy flow is sequentially processed by steam energy flow and chemical energy flow input; the pulping process energy flow is used to process the pulping link; the papermaking process energy flow is used to process the papermaking link; and the fiber process energy flow is used to process the fiber production link.

8. The biogas energy multi-stage combined supply and digital energy management method according to claim 1 is characterized in that: The biogas parameters include biogas volume and methane ratio in biogas, and the steam parameters include calorific value, mass flow rate, steam temperature and steam pressure; The raw materials of papermaking enterprises are processed through three processes: pulping, fiber making and paper making to produce biogas, and the CH4 content in the biogas is between 45-50%. The monitoring range of the steam parameters includes: temperature monitoring range of 0-300°C, with an accuracy of ±1°C; The pressure monitoring range is 0-5MPa with an accuracy of ±0.01MPa; the flow monitoring uses an ultrasonic flow meter with an accuracy of ±0.5%.

9. The biogas energy multi-stage combined supply and digital energy management method according to claim 1 is characterized in that: The energy flow conversion relationship of the multi-energy flow system includes: In the papermaking process, the low-grade heat energy and steam heat energy with an evaporation pressure of 0.3MPa in the pulping process, the high-temperature steam with an evaporation pressure of 0.8MPa in the papermaking process and the high-temperature steam driving the steam turbine generator, the steam heat energy after the steam turbine, the output steam heat energy pressure is 0.12MPa; In the pulping process, the high-quality heat energy of the fiber process, the high-temperature steam of the pulping process and the high-temperature steam driving the steam turbine generator, the steam heat energy after the steam turbine, the output steam heat energy pressure is 0.12MPa; In the fiber process, the high-quality heat energy and evaporation pressure of the pulping process are 0.8MPa high-temperature steam and high-temperature steam drive the turbine generator. The steam heat energy after the steam turbine has an output steam heat energy pressure of 0.12MPa; In the multi-energy flow system, valves are provided between the biomass slurry tower, gas production pool, heat storage buffer tank, steam pipeline of the biomass slurry tower, steam heating network of the biomass slurry tower and the steam co-supply heating network, and the valves are controlled by a PLC controller.

10. Biogas energy multi-level supply and digital energy management system, characterized by: include: Distributed sensor network, used to obtain biogas parameters, steam parameters and waste heat temperature parameters generated in the pulping, fiber making and paper making processes of papermaking enterprises; a multidimensional parameter decision processing unit, configured to perform hierarchical processing on the biogas based on the biogas parameters through a multidimensional parameter hierarchical decision tree, wherein the multidimensional parameter hierarchical decision tree includes a methane concentration diversion layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value assessment layer; a temperature matching calculation unit, configured to calculate a first temperature difference and a second temperature difference according to the steam parameter and the waste heat temperature parameter, and form a temperature matching relationship based on the first temperature difference and the second temperature difference; an energy path determination unit, configured to determine an energy utilization path of the biogas based on the temperature matching relationship and the hierarchical processing result of the multi-dimensional parameter hierarchical decision tree, and convert the biogas into electrical energy, heat energy, cold energy, steam energy, high-quality suction air, and low-quality suction air according to the energy utilization path, thereby forming a multi-energy flow system; A multi-energy cascade supplier, used to transmit the energy flow in the multi-energy flow system, consisting of a plurality of multi-energy cascade suppliers, with cold energy use and heat energy use provided at the output end of the multi-energy cascade supplier, and cold energy input, heat energy input and steam provided at the input end of the multi-energy cascade supplier; A multi-stage valve network, including multiple valves arranged between the biomass slurry tower, the gas production pool, and the heat storage buffer tank, wherein the valves are controlled by a PLC controller; The digital management unit is used to process and summarize the energy flow data in the multi-energy flow system in real time, compare it with the energy demand, and upload the comparison results to the cloud platform for management, so as to realize the digital management of multi-level cascade biogas energy.

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