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

Abstract

The invention relates to the field of energy management, in particular to a marsh gas energy multi-cascade supply and digital energy management method and system.According to the method, marsh gas is graded through a multi-dimensional parameter hierarchical decision tree, and a methane concentration shunting layer, a volume analysis layer, a temperature difference comparison layer and a calorific value evaluation layer are included; based on steam parameters and waste heat temperature parameters, temperature difference is calculated, a temperature matching relation is formed, according to the relation and a decision tree processing result, an energy utilization path of biogas is determined and converted into electric energy, heat energy, cold energy, steam energy, high-quality induced draft and low-quality induced draft, a multi-energy-flow system is formed, energy flow data of the system are processed and summarized in real time, and the energy utilization rate of the system is improved. According to the method, the energy utilization efficiency is improved, the marsh gas is utilized in a refined and graded mode, the optimal utilization path is selected according to the quality characteristics of the marsh gas, and the energy value of marsh gas of different qualities is maximized.

Description

Technical Field

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

[0002] The paper-making industry is one of the industries with large energy consumption, and a large amount of biogas resources are generated in the processes of pulping, fiber making, and paper making. The traditional biogas utilization methods mainly include simple combustion for power generation or heating, which fail to fully utilize the potential value of biogas energy and have low energy utilization efficiency.

[0003] The existing biogas utilization technologies have the following problems: First, there is a lack of refined analysis and hierarchical utilization of biogas quality, and it is impossible to carry out targeted treatment according to the different characteristics of biogas; second, the matching degree between biogas energy and the energy demand of the paper-making process is not high, resulting in a waste phenomenon of high-grade energy being used at a low grade; third, there is a lack of an accurate recovery and reuse mechanism for waste heat resources, causing energy waste; finally, there is a lack of a digital and intelligent energy management system, and it is impossible to realize real-time monitoring and optimal allocation of the energy flow.

[0004] Therefore, there is an urgent need for a technical solution that can carry out refined hierarchical utilization of biogas, realize multi-stage energy combined supply, and have digital management capabilities to improve the energy utilization efficiency and economic benefits of the paper-making industry. Summary of the Invention

[0005] The object of the present invention is to provide a method and system for multi-stage combined supply of biogas energy and digital energy management, which realizes 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 waste heat distribution driven by economy, realizes precise control of the energy flow direction through a precise control execution and valve network coordination system, and realizes the intelligence of energy management through a closed-loop optimization system integrated with a cloud platform, thereby improving the energy utilization efficiency and economic benefits of biogas energy in the paper-making industry.

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

[0007] Obtaining biogas parameters, steam parameters, and waste heat temperature parameters generated in the processes of pulping, fiber making, and paper making in a paper-making enterprise;

[0008] Based on the biogas parameters, carrying out hierarchical treatment of biogas through a multi-dimensional parameter hierarchical decision tree, where the multi-dimensional parameter hierarchical decision tree includes a methane concentration shunt layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value evaluation layer;

[0009] Calculate the first temperature difference and the second temperature difference according to the steam parameters and the waste heat temperature parameters, and form 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, determine the energy utilization path of biogas, and convert biogas into electric 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] Perform real-time processing and summarization of the energy flow data in the multi-energy flow system, compare it with the energy demand, and upload the comparison result to the cloud platform for management to achieve digital management of multi-stage combined supply biogas energy.

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

[0013] In the methane concentration shunt layer, obtain the methane proportion in biogas. When the methane proportion is greater than the preset threshold, enter the high-quality biogas treatment path. When the methane proportion is less than the preset threshold, enter the low-quality biogas treatment path, where the preset threshold is 80%;

[0014] In the volume analysis layer, obtain the biogas volume. When the biogas volume is greater than the preset volume threshold, use biogas directly as combustion-supporting air. When the biogas volume is less than the preset volume threshold, enter the temperature difference comparison layer, where the preset volume threshold is 100 m³ / h;

[0015] In the temperature difference comparison layer, obtain the biogas temperature and compare it with the first temperature difference and the second temperature difference. When the biogas temperature is less than the first temperature difference, use biogas as supplementary combustion-supporting air. When the biogas temperature is greater than the first temperature difference and less than the second temperature difference, mix biogas with steam and then burn it. When the biogas temperature is greater than the second temperature difference, directly burn and utilize biogas through an efficient combustion channel;

[0016] In the calorific value evaluation layer, when the difference between the biogas temperature and the second temperature difference is greater than the preset temperature difference threshold, obtain the lower calorific value and the lower combustion calorific value of biogas, and determine the final treatment method of biogas according to the lower calorific value and the lower combustion calorific value, where the preset temperature difference threshold is 10 °C.

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

[0018] Obtain the lower calorific value and the lower combustion calorific value of biogas;

[0019] When the lower calorific value is less than the first calorific value threshold and the lower combustion calorific value is less than the second calorific value threshold, use biogas as supplementary combustion-supporting air to the biomass combustion-supporting air channel;

[0020] When the lower calorific value is greater than the first calorific value threshold and the lower combustion calorific value is less than the second calorific value threshold, after mixing biogas with steam, it is burned through the combustion calorific value channel, and then through the superheated steam supply channel, the burned gas is supplemented into the steam channel of the biomass pulp tower;

[0021] When the lower calorific value is less than the first calorific value threshold and the lower combustion calorific value is greater than the second calorific value threshold, after mixing biogas with steam, it is burned through the combustion calorific value channel, and then through the superheated steam supply channel, the burned gas is supplemented into the steam channel of the biomass pulp tower;

[0022] When the lower calorific value is greater than the first calorific value threshold and the lower combustion calorific value is greater than the second calorific value threshold, the biogas is supplemented into the biomass combustion air channel as combustion-supporting air;

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

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

[0025] Obtain the temperature required for papermaking and the waste heat temperature before waste heat utilization in the papermaking workshop, match the temperature required for papermaking with the waste heat temperature before waste heat utilization, and obtain the first temperature difference;

[0026] Obtain the temperature required for papermaking and the waste heat temperature after waste heat recovery in the papermaking workshop, match the temperature required for papermaking with the waste heat temperature after waste heat recovery, and obtain the second temperature difference;

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

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

[0029] Obtain the steam temperature and steam pressure. When the steam pressure is greater than the preset pressure threshold and the steam temperature is greater than the preset temperature threshold, steam is supplemented into the steam pipeline of the biomass pulp tower. When the steam pressure is less than the preset pressure threshold or the steam temperature is less than the preset temperature threshold, the steam supply to the steam pipeline is stopped;

[0030] Among them, the preset pressure threshold is 3 bar, and the preset temperature threshold is 135 °C;

[0031] The high-quality heat energy of 0.8 MPa drives the steam turbine to generate electricity, and the power generation efficiency is 55%, and the heat energy of 0.12 MPa is generated to supply steam;

[0032] Medium-grade thermal energy of 0.3 MPa is used for chemicals in the pulping process and pulp dilution in the papermaking process;

[0033] Low-grade thermal energy of 50 - 70 °C is used in a low-pressure organic Rankine cycle. In the form of a heat pump, the heat of the steam thermal energy generated by driving is used to supply the heat of the low-temperature hot water for the fiberboard pulping process.

[0034] Preferably, the energy economy evaluation and distribution process based on the multi-energy flow system includes:

[0035] Based on the gas state parameters and waste heat temperature in the gas production pool, according to the conversion relationship between waste heat and electricity price, determine the heat prices of co-generated steam and purchased steam;

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

[0037] Determine the co-generation ratio of co-generated steam and purchased steam according to the ratio of the calorific value of co-generated steam to the calorific value of steam required for waste heat co-generation;

[0038] Multiply the co-generation ratio by the heat price to obtain the gas purchase price and sales price;

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

[0040] When the gas purchase price is lower than the sales price, prepare steam from the waste heat and supply it through the heat network;

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

[0042] Preferably, the electric energy, cold energy, thermal energy, steam energy, high-grade suction air, and low-grade suction wind energy generated in the multi-energy flow system are sequentially transmitted to the cold energy usage and thermal energy usage demand ends of the papermaking equipment;

[0043] A multi-energy connector is set in the multi-level co-supplier to connect the output end and input end of the multi-level co-supplier, facilitating the input and output of multi-energy flow;

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

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

[0046] After the raw materials of the paper-making enterprise go through three technological processes of pulping, fiber-making, and paper-making, biogas is generated, and the content of CH4 in the biogas is between 45% and 50%;

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

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

[0049] In the paper-making process, the low-grade thermal energy of the pulping process, the steam thermal energy with an evaporation pressure of 0.3 MPa, the high-temperature steam with an evaporation pressure of 0.8 MPa in the paper-making process, and the high-temperature steam driving the steam turbine generator. After the steam thermal energy passes through the steam turbine, the output steam thermal energy pressure is 0.12 MPa;

[0050] In the pulping process, for the high-grade thermal energy of the fiber process, the high-temperature steam in the pulping process, and the high-temperature steam driving the steam turbine generator. After the steam thermal energy passes through the steam turbine, the output steam thermal energy pressure is 0.12 MPa;

[0051] In the fiber process, for the high-grade thermal energy of the pulping process, the high-temperature steam with an evaporation pressure of 0.8 MPa, and the high-temperature steam driving the steam turbine generator. After the steam thermal energy passes through the steam turbine, the output steam thermal energy pressure is 0.12 MPa;

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

[0053] The biogas energy multi-stage combined supply and digital energy management system includes:

[0054] A distributed sensing network for obtaining biogas parameters, steam parameters, and waste heat temperature parameters generated in the pulping, fiber-making, and paper-making technological processes of the paper-making enterprise;

[0055] A multi-dimensional parameter decision processing unit for classifying biogas based on the biogas parameters through a multi-dimensional parameter hierarchical decision tree, and the multi-dimensional parameter hierarchical decision tree includes a methane concentration shunt layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value evaluation layer;

[0056] A temperature matching calculation unit, configured to calculate a first temperature difference and a second temperature difference according to the steam parameters and the waste heat temperature parameters, 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 the energy utilization path of biogas based on the temperature matching relationship and the hierarchical processing result of the multi-dimensional parameter hierarchical decision tree, and convert biogas into electric energy, heat energy, cold energy, steam energy, high-quality suction air and low-quality suction air according to the energy utilization path, forming a multi-energy flow system;

[0058] A multi-level cascade supplier, configured to transmit the energy flow in the multi-energy flow system, which consists of multiple multi-level cascade suppliers. At the output end of the multi-level cascade supplier, there are cold energy utilization and heat energy utilization, and at the input end of the multi-level cascade supplier, there are cold energy input, heat energy input and steam;

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

[0060] A digital management unit, configured to perform real-time processing and summarization of the energy flow data in the multi-energy flow system, compare it with the energy demand, and upload the comparison result to the cloud platform for management, realizing the digital management of the multi-stage cascade supply biogas energy.

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

[0062] 1. Improve energy utilization efficiency: Through the refined hierarchical utilization of biogas by the multi-dimensional parameter hierarchical decision tree, select the best utilization path for biogas according to its quality characteristics, maximize the energy value of biogas with different qualities, and improve the 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, precisely match the energy quality and usage demand, avoid the waste phenomenon of high-grade energy being used at a low grade, and improve the rationality of energy utilization.

[0064] 3. Optimize energy economy: Through the dynamic heat price calculation and the waste heat distribution mechanism driven by economy, organically combine technical optimization and economic optimization, realize the comprehensive optimization of energy utilization, and improve the economic benefit by 15 - 25%.

[0065] 4. Improve the system control accuracy: Through the precise coordinated control of the valve network, achieve precise regulation of the energy flow direction, ensure the stable and reliable operation of the system, and shorten the response time to within 2 seconds.

[0066] 5. Achieve intelligent energy management: Through the closed-loop optimization system integrated by the cloud platform, realize the digitization and intelligence of energy management. The system has self-optimization ability, reduces manual intervention, and improves management efficiency by 35-45%. Brief Description of the Drawings

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

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

[0069] Figure 3 is the working flow chart of the temperature difference calculation and energy matching module of the present invention;

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

[0071] Figure 5 is the data flow schematic diagram of the digital management unit of the present invention. Detailed Embodiment

[0072] Please refer to the attached Figures 1-5 , the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0073] As Figure 1 shown, the present invention provides a biogas energy multi-stage cascade supply and digital energy management method and system. The system includes a distributed sensing network 1, a multi-dimensional parameter decision processing unit 2, a temperature matching calculation unit 3, an energy path determination unit 4, a multi-level cascade supplier 5, a multi-level valve network 6, and a digital management unit 7. The system is applied to a paper-making enterprise for the efficient utilization and intelligent management of biogas generated in the three technological processes of pulp making, fiber making, and paper making.

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

[0075] First, obtain the biogas parameters, steam parameters, and waste heat temperature parameters generated in the pulping, fiber making, and papermaking processes of the paper-making enterprise through the distributed sensing network 1. Among them, the biogas parameters include the biogas volume and the methane proportion in the biogas, and the steam parameters include the calorific value, mass flow rate, steam temperature, and steam pressure. In a specific embodiment of the present invention, the distributed sensing network 1 includes a biogas production tank monitoring subsystem, a steam parameter monitoring subsystem, and a waste heat temperature monitoring subsystem. The biogas production tank monitoring subsystem is arranged in the main tank and the auxiliary tank of the biogas production tank, and is equipped with a methane concentration meter, a hydrogen concentration meter, a carbon dioxide concentration meter, and an oxygen concentration meter. The acquisition frequency is 30 seconds / time, and the data acquisition accuracy is methane concentration ±0.5%, gas flow ±1.0%. The steam parameter monitoring subsystem installs a thermometer, a pressure gauge, and a flow meter at key pipeline nodes. The temperature monitoring range is 0 - 300 °C, the accuracy is ±1 °C, the pressure monitoring range is 0 - 5 MPa, the accuracy is ±0.01 MPa, and the flow monitoring uses an ultrasonic flow meter with an accuracy of ±0.5%. The waste heat temperature monitoring subsystem sets up a temperature sensor array in the paper-making workshop to monitor the temperature change before and after waste heat utilization.

[0076] Secondly, the multi-dimensional parameter decision-making processing unit 2 classifies the biogas through a multi-dimensional parameter hierarchical decision tree based on the obtained biogas parameters. As Figure 2 shown, the multi-dimensional parameter hierarchical decision tree includes a methane concentration shunt layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value evaluation layer. The methane concentration shunt layer conducts a preliminary classification according to the methane proportion in the biogas, the volume analysis layer further subdivides according to the biogas volume, the temperature difference comparison layer selects the biogas treatment path in combination with the temperature matching relationship, and the calorific value evaluation 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 based on the steam parameters and the waste heat temperature parameters, and forms a temperature matching relationship based on these two temperature differences. As Figure 3 shown, the first temperature difference reflects the difference between the temperature required for papermaking and the temperature before waste heat utilization, and the second temperature difference reflects the difference between the temperature required for papermaking and the temperature after waste heat recovery. These two temperature differences provide key indicators for the matching of energy demand and supply. In the embodiment of the present invention, when the temperature difference is greater than zero, it indicates that the energy is insufficient and energy needs to be supplemented; when the temperature difference is less than zero, it indicates that the energy is excessive and the energy can be recycled.

[0078] Next, the energy path determination unit 4 determines the energy utilization path of the biogas based on the temperature matching relationship and the classification result of the multi-dimensional parameter hierarchical decision tree, and converts the biogas into electric energy, heat energy, cold energy, steam energy, high-quality suction air, and low-quality suction air according to the energy utilization path, forming a multi-energy flow system. As Figure 4As shown, the energy conversion relationships in the multi-energy flow system include 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, etc.

[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, realizing the digital management of the multi-cascaded biogas energy. As Figure 5 shown, the digital management unit 7 realizes the closed-loop management of energy data acquisition, processing, analysis, and optimization. Preferably, the digital management unit 7 adopts a hierarchical architecture, including a data storage layer, a data analysis layer, and a decision support layer, which can realize the digitalization and intelligence of 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 shunt layer, the methane proportion in the biogas is obtained through a methane concentration meter. When the methane proportion is greater than the preset threshold, it enters the high-quality biogas treatment path. When the methane proportion 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 proportion exceeds 80%, the combustion efficiency and calorific value of the biogas are significantly improved, making it suitable for direct utilization as a high-quality fuel. When the methane proportion is lower 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, the biogas volume is obtained through a flow meter. When the biogas volume is greater than the preset volume threshold, the biogas is directly used as combustion-supporting air. When the biogas volume is less than the preset volume threshold, it enters the temperature difference comparison layer for further analysis. Preferably, the preset volume threshold is set to 100 m³ / h. This threshold is determined based on actual application experience. When the biogas production exceeds 100 m³ / h, it is sufficient to be used as the main fuel. When the production is lower than this threshold, more refined allocation needs to be combined with the temperature demand to achieve the optimal utilization of energy.

[0083] In the temperature difference comparison layer, the biogas temperature is obtained and compared with the first temperature difference and the second temperature difference, forming three treatment paths: when the biogas temperature is less than the first temperature difference, the biogas is used as supplementary combustion-supporting 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 a high-efficiency combustion channel. This decision-making mechanism based on temperature difference can achieve the precise matching of energy and avoid energy waste.

[0084] In the calorific value evaluation layer, when the difference between the biogas temperature and the second temperature difference is greater than the preset temperature difference threshold, the lower calorific value and the lower combustion calorific value of the biogas are obtained, and the final treatment method of the biogas is determined based on these two parameters. Preferably, the preset temperature difference threshold is set to 10°C. The selection of this threshold takes into account the efficiency of heat energy transfer and the allowable temperature difference range in actual engineering. When the temperature difference exceeds 10°C, entering the calorific value evaluation link can more precisely determine the energy utilization path.

[0085] In addition, to ensure the rationality of the decision-making, the present invention also sets up a path priority mechanism: the first priority is safety consideration to ensure the stable operation of the system; the second priority is energy efficiency, and the path with high energy utilization efficiency is preferentially selected; the third priority is economy, and the path with the best economic benefit is selected under the condition of meeting the first two conditions.

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

[0087] First, the lower calorific value and the lower combustion calorific value of the biogas are obtained through calorific value measuring equipment. The lower calorific value reflects the energy release amount of the combustible components in the biogas, and the lower combustion calorific value reflects the heat energy conversion efficiency during the combustion process. These two parameters jointly determine the energy value and the best utilization method of the biogas.

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

[0089] When the lower calorific value is greater than the first calorific value threshold and the lower combustion calorific value is less than the second calorific value threshold, the biogas is mixed with steam and then burned through the combustion calorific value channel, and then through the superheated steam supply channel, the burned gas is supplemented into the steam channel of the biomass pulp tower. In this case, the biogas has a relatively high energy content, but the combustion efficiency is not high. By mixing with steam, its utilization efficiency can be improved.

[0090] When the lower calorific value is less than the first calorific value threshold and the lower combustion calorific value is greater than the second calorific value threshold, the biogas is also mixed with steam and burned through the combustion calorific value channel, and then transported through the superheated steam supply channel. In this case, although the energy content of the biogas is not high, the combustion efficiency is relatively high. Mixing with steam can give full play to its combustion efficiency advantage.

[0091] When the lower calorific value is greater than the first calorific value threshold and the lower combustion calorific value is greater than the second calorific value threshold, the biogas is directly burned and utilized through the high-efficiency combustion channel. In this case, both the energy content and the combustion efficiency of the biogas are relatively high, and it is suitable for direct use as the main fuel.

[0092] Preferably, the first calorific value threshold is set to 21000 kj / m³, and the second calorific value threshold is set to 24000 kj / m³. The setting of these two thresholds is based on the actual experience of biogas energy utilization and engineering application data, which can effectively distinguish biogas of different qualities and select the best utilization path for it.

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

[0094] First, the temperature matching calculation unit 3 obtains the temperature required for papermaking and the waste heat temperature before waste heat utilization in the papermaking workshop. In a specific embodiment of the present invention, the temperature required for papermaking is usually 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 usually in the range of 80 - 120 °C, depending on the 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, and calculates the first temperature difference. The calculation formula is:

[0096] ,

[0097] Among them, is the first temperature difference, with the unit of °C; is the temperature required for papermaking, with the unit of °C; is the temperature before waste heat utilization, with the unit of °C. This formula represents the difference between the temperature required for papermaking and the temperature before waste heat utilization, reflecting the gap between the energy demand and the 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, and calculates the second temperature difference. The calculation formula is:

[0100] ,

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

[0102] These two temperature differences provide important reference indicators for energy matching. When the temperature difference is greater than zero, it indicates insufficient energy and energy needs to be supplemented; when the temperature difference is less than zero, it indicates excess energy and the energy can be recycled. Through this energy distribution mechanism driven by temperature difference, precise energy matching can be achieved, avoiding energy waste.

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

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

[0105] First, the steam temperature and steam pressure are obtained through the steam parameter monitoring subsystem. In the 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 - 5 MPa and an accuracy of ±0.01 MPa.

[0106] Then, based on the obtained steam parameters, it is determined whether steam needs to be supplemented to the biomass pulp tower. When the steam pressure is greater than the preset pressure threshold and the steam temperature is greater than the preset temperature threshold, steam is supplemented to the steam pipeline of the biomass pulp tower; when the steam pressure is less than the preset pressure threshold or the steam temperature is less than the preset temperature threshold, the supply of steam 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. The setting of these two thresholds is based on the actual requirements of the papermaking process and the requirements for the safe operation of the equipment, ensuring that the supplied steam can meet the process requirements while ensuring the safe and stable operation of the system.

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

[0108] Secondly, medium-quality heat energy of 0.3 MPa is used for chemical treatment in the pulping process and pulp dilution in the papermaking process. The medium-quality heat energy mainly comes from the medium-temperature steam generated in the pulping process, and the temperature is usually in the range of 140 - 160 °C. This part of the heat energy is used to provide a medium-temperature heat source required by the process to meet the temperature requirements of specific process links.

[0109] Finally, through low-grade thermal energy at 50 - 70 °C, using a low-pressure organic Rankine cycle, the heat energy of steam is utilized in the form of a heat pump to drive the generation of low-temperature hot water for use in the fiberboard pulping process. The low-grade thermal energy mainly comes from the low-temperature waste heat generated in the pulping process, and its quality can be improved through the organic Rankine cycle to achieve cascaded utilization of energy.

[0110] In the organic Rankine cycle, an organic working fluid suitable for a low-temperature heat source of 50 - 70 °C (such as R245fa or R134a) is selected as the working medium. It evaporates after absorbing low-grade thermal energy in the evaporator, the steam drives the expander to do work, then releases heat and condenses into a liquid in the condenser, and finally is pumped back to the evaporator to complete the cycle. This process can convert low-grade thermal energy into a more valuable form of energy and improve energy utilization efficiency.

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

[0112] First, the gas state parameters in the biogas digester are obtained through the biogas digester monitoring subsystem, and the waste heat temperature is obtained through the waste heat temperature monitoring subsystem. In the specific embodiment of the present invention, the gas state parameters include methane content, gas flow rate, temperature, pressure, etc.; the waste heat temperature is obtained through the temperature sensor array set in the paper-making workshop, with an accuracy of ±1 °C.

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

[0114] ,

[0115] Among them, is the thermal price of co-generated steam, with the unit of yuan / ton; is the conversion coefficient, dimensionless, and usually takes a value range of 0.8 - 0.9; is the biogas calorific value, with the unit of kj / m is the current electricity price, with the unit of yuan / kWh; is the steam calorific value, with the unit of kj / kg; is the temperature correction coefficient, dimensionless, and usually takes a value range of 0.1 - 0.2; is the waste heat temperature, with the unit of °C; is the maximum waste heat temperature, with the unit of °C, usually set to 200 °C. This formula comprehensively considers factors such as energy price, calorific value, and temperature, and calculates the comprehensive thermal price of co-generated steam.

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

[0117] Then, the digital management unit 7 determines the heat price conversion ratio according to the ratio of the biogas calorific value in the biogas production tank to the combined heat and power steam calorific value. The calculation formula for the heat price conversion ratio is:

[0118] ,

[0119] Where, is the heat price conversion ratio, dimensionless; is the biogas calorific value, in kj / m³; is the combined heat and power steam calorific value, in kj / kg. This ratio represents the energy ratio of unit biogas to unit combined heat and power steam, reflecting the energy conversion efficiency.

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

[0121] ,

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

[0123] Then, the product of the combined heat and power ratio and the heat price gives the gas purchase price and the sales price. The calculation formula for the gas purchase price is:

[0124] ,

[0125] Where, is the gas purchase price, dimensionless, representing the relative price index for purchasing biogas; is the heat price conversion ratio, dimensionless; is the combined heat and power ratio, dimensionless; is the heat price ratio, dimensionless. This calculation result is used to compare with the sales price to determine the most economical energy utilization path.

[0126] Sales price , dimensionless, representing the relative price index for selling biogas, usually market - priced and affected by various factors, including regional supply - demand relationship, seasonal changes, etc.

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

[0128] When the gas purchase price is higher than the sales price, the waste heat is sold. In this case, selling the waste heat is more economical than self - use;

[0129] When the gas purchase price is lower than the sales price, steam is prepared from the waste heat and supplied through the heat network. In this case, self - using the waste heat is more economical than selling it;

[0130] When the gas purchase price is equal to the sales price, steam is prepared from the waste heat and transported through the steam pipeline. In this case, the two options have comparable economics and can be flexibly selected according to the actual situation.

[0131] In a specific embodiment of the present invention, assume that the calorific value of biogas is 20000 kj / m³, the calorific value of co - generated steam is 2500 kj / kg, the calorific value of steam required for waste heat co - generation is 2300 kj / kg, the current electricity price is 0.6 yuan / kWh, the market purchase 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 into the above formula for calculation:

[0132] Co - generated steam heat price 0.0675)=4.57 yuan / ton

[0133] Heat price ratio ;

[0134] Heat price conversion ratio ;

[0135] Co - generation ratio ;

[0136] Gas purchase price $P_{buy} = 8 \times 1.09 \times 0.023 = 0.2$

[0137] Assume the market sales price Assume the market sales price , since , so choosing the plan to sell the waste heat is more reasonable economically.

[0138] The energy transmission of the multi - energy flow system and the working process of the multi - level cascade supplier in the present invention include:

[0139] First, the electric energy, cold energy, heat energy, steam energy, high-quality suction air, and low-quality suction wind energy generated in the multi-energy flow system are sequentially transmitted to the cold energy usage and heat energy usage demand ends of the papermaking equipment. In the embodiments of the present invention, the multi-energy flow system realizes the directional transmission of energy through a specially designed pipeline network and control system, ensuring the efficient utilization of energy and reducing transmission losses.

[0140] Secondly, a multi-energy connector is provided in the multi-level cascade supplier 5 for connecting the output end and the input end of the multi-level cascade supplier, facilitating the input and output of multi-energy flow. The multi-energy connector adopts a standardized design to ensure the efficient conversion and transmission between different energy forms, improving the system integration and operation stability.

[0141] Then, the multi-energy flow system includes sequentially dividing the energy flow into five parts: steam energy flow, pulping energy flow, pulping process energy flow, papermaking process energy flow, and fiber process energy flow, forming a complete energy utilization chain. The steam energy flow drives the steam turbine generator by heat energy, and the efficiency of steam turbine power generation is 55%. The steam heat energy pressure after the steam turbine is 0.12 MPa, and this part of the steam continues to be used in the downstream process to achieve the cascaded utilization of energy.

[0142] The pulping energy flow sequentially undergoes input processing of the steam energy flow and chemical energy flow to provide the required energy for the pulping process. The pulping process energy flow is used to process the pulping link, including processes such as wood chip cooking, washing, and screening. The papermaking process energy flow is used to process the papermaking link, including processes such as pulp forming, pressing, and drying. The fiber process energy flow is used to process the fiber production link, including processes such as fiber preparation and forming.

[0143] During the energy transmission process, the system adopts the principle of "temperature drop drive and pressure difference drive" to ensure the efficient transmission of energy. At the same time, through the precise control of the multi-level cascade supplier, the directional distribution and cascaded utilization of energy are realized, improving the overall energy utilization efficiency.

[0144] The detailed description of the biogas parameters and steam parameters in the present invention includes:

[0145] The biogas parameters include the biogas volume and the methane proportion in the biogas. The biogas volume reflects the quantity of biogas generated and is an important parameter determining the biogas utilization method; the methane proportion in the biogas reflects the quality and energy density of the biogas, directly affecting the calorific value and utilization efficiency of the biogas. In the specific embodiments of the present invention, the biogas volume is measured by a flow meter with an accuracy of ±1.0%; the methane proportion is measured by a methane concentration meter with an accuracy of ±0.5%.

[0146] Steam parameters include calorific value, mass flow rate, steam temperature, and steam pressure. The calorific value reflects the energy contained in unit steam; the mass flow rate reflects the supply of steam; the steam temperature and pressure determine the quality and applicable working conditions of the steam. In the present invention, the steam calorific value is obtained through heat calculation; the mass flow rate is measured by a flowmeter; the steam temperature is measured by a thermometer, with a range of 0 - 300 °C and an accuracy of ±1 °C; the steam pressure is measured by a pressure gauge, with a range of 0 - 5 MPa and an accuracy of ±0.01 MPa.

[0147] Preferably, after the raw materials of the paper-making enterprise go through three technological processes of pulping, fiber-making, and paper-making, biogas is generated, and the content of CH4 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 paper-making industry. Compared with the biogas generated in other industries (such as the biogas in the livestock industry, where the CH4 content is usually between 60 - 70%), the methane content of the biogas generated in the paper-making industry is relatively low, but through the technical solution of the present invention, efficient utilization can still be achieved.

[0148] In the present invention, the energy flow conversion relationship of the multi-energy flow system includes energy conversion in three main technological processes:

[0149] In the paper-making process, the low-grade thermal energy of the pulping process, the steam thermal energy with an evaporation pressure of 0.3 MPa, the high-temperature steam with an evaporation pressure of 0.8 MPa in the paper-making process, and the high-temperature steam driving the steam turbine generator are used to achieve efficient utilization of energy. After passing through the steam turbine, the steam thermal energy has an output steam thermal energy pressure of 0.12 MPa and is continued to be used in subsequent processes. This multi-stage utilization mode significantly improves the comprehensive utilization efficiency of energy.

[0150] In the pulping process, the high-grade thermal energy of the fiber process, the high-temperature steam in the pulping process, and the high-temperature steam driving the steam turbine generator are also used to achieve cascade utilization of energy. After passing through the steam turbine, the steam thermal energy has an output steam thermal energy pressure of 0.12 MPa and is used to meet the requirements of other processes. This energy coupling method reduces energy waste and improves the overall efficiency of the system.

[0151] In the fiber process, the high-grade thermal energy of the pulping process, the high-temperature steam with an evaporation pressure of 0.8 MPa, and the high-temperature steam driving the steam turbine generator are further used to achieve comprehensive utilization of energy. After passing through the steam turbine, the steam thermal energy has an output steam thermal energy pressure of 0.12 MPa and is continued to be put into use.

[0152] In the entire multi-energy flow system, valves are provided between the biomass pulp tower, the gas production tank, the heat storage buffer tank, the steam pipeline of the biomass pulp tower, the steam heat network of the biomass pulp tower, and the heat network for steam co-supply, forming a complete control network. All valves are controlled by a PLC controller, realizing centralized control and precise adjustment of the system.

[0153] The PLC controller uses industrial-grade control equipment, which has high reliability and real-time performance and can monitor and adjust the system operation status in real time. In a specific embodiment of the present invention, the PLC controller adopts a modular design, including a CPU module, a power supply module, an input / output module, a communication module, etc., and communicates with each sensor and actuator through industrial Ethernet. The communication cycle is 50 ms to ensure the timeliness and accuracy of control.

[0154] The biogas energy multi-cascade supply and digital energy management system provided by the present invention includes the following units:

[0155] The distributed sensing network 1 is used to obtain biogas parameters, steam parameters, and waste heat temperature parameters generated in the papermaking enterprise's pulp making, fiber making, and papermaking processes. The distributed sensing network adopts a three-layer architecture: the field layer includes various sensors and data acquisition devices; the network layer includes industrial Ethernet and wireless sensor networks; the management layer includes a data server and a monitoring terminal. This hierarchical architecture improves the reliability and scalability of the system.

[0156] The multi-dimensional parameter decision processing unit 2 is used to classify biogas based on biogas parameters through a multi-dimensional parameter hierarchical decision tree. The multi-dimensional parameter decision processing unit adopts a modular design, including a parameter preprocessing module, a decision tree execution module, and a result output module. The decision tree structure is implemented by software and can be adjusted and optimized according to actual needs.

[0157] 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 waste heat temperature parameters and form a temperature matching relationship. The temperature matching calculation unit realizes temperature difference calculation and matching analysis through a special algorithm, providing a key basis for energy distribution.

[0158] The energy path determination unit 4 is used to determine the energy utilization path of biogas based on the temperature matching relationship and the classification processing results of the multi-dimensional parameter hierarchical decision tree, convert biogas into multiple energy forms, and form a multi-energy flow system. The energy path determination unit realizes the optimal decision of energy distribution through an optimization algorithm to ensure the maximization of the system operation efficiency.

[0159] The multi-level cascade supplier 5 is used to transmit the energy flow in the multi-energy flow system and is composed of multiple multi-level cascade suppliers. Each multi-level cascade supplier is provided with an input end and an output end. The output end is provided with cold energy use and heat energy use interfaces, and the input end is provided with cold energy input, heat energy input, and steam interfaces. The multi-level cascade supplier adopts a standardized design, which is convenient for system integration and expansion.

[0160] The multi-stage valve network 6 includes multiple valves disposed between the biomass pulp tower, the gas production tank, and the heat storage buffer tank. All valves are controlled by a PLC controller to achieve precise control and regulation of the system. The multi-stage valve network adopts a redundant design, improving the reliability and safety of the system.

[0161] The digital management unit 7 is used to perform real-time processing and summarization of the energy flow data in the multi-energy flow system, compare it with the energy demand, and upload the comparison result to the cloud platform for management. The digital management unit adopts a cloud-edge-terminal architecture to achieve distributed processing and centralized management of data. The cloud platform provides data storage, analysis, and decision support; the edge computing node realizes data preprocessing and real-time response; the terminal device is responsible for data collection and execution.

[0162] During the implementation of the system, data exchange and collaborative work are achieved between the units through standardized interfaces and communication protocols. The system adopts a modular design, facilitating maintenance and upgrading. At the same time, the system is also equipped with security mechanisms, including data encryption, access control, and anomaly detection, etc., to ensure the security and reliability of the system operation.

[0163] In summary, the biogas energy multi-stage cascade supply and digital energy management method and system provided by the present invention achieve refined hierarchical utilization of biogas through a multi-dimensional parameter hierarchical decision tree, achieve precise matching of energy through a temperature difference-driven energy distribution mechanism, achieve economic optimization of energy utilization through dynamic heat price calculation and waste heat distribution driven by economy, achieve precise control of the energy flow direction through precise control execution and valve network coordination system, and achieve intelligent energy management through a closed-loop optimization system integrated on the cloud platform, thereby improving the utilization efficiency and economic benefits of biogas energy in the paper industry.

[0164] The industrial application prospect of the present invention is broad. It is not only applicable to the paper industry, but also can be extended to other industrial fields that generate biogas, such as the food processing, brewing, sugar-making industries, etc., providing a new technical approach for industrial energy conservation and emission reduction.

[0165] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all should be covered by the protection scope of the present invention.

Claims

1. A multi - stage combined supply method of biogas energy and digital energy management method, characterized in that Including: Obtaining biogas parameters, steam parameters, and waste heat temperature parameters generated in the pulping, fiber making, and papermaking processes of a paper-making enterprise; Based on the biogas parameters, classifying the biogas through a multi-dimensional parameter hierarchical decision tree, where the multi-dimensional parameter hierarchical decision tree includes a methane concentration shunt layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value evaluation layer; According to the steam parameters and the waste heat temperature parameters, calculating a first temperature difference and a second temperature difference, 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 classification result of the multi-dimensional parameter hierarchical decision tree, determining the energy utilization path of the biogas, and converting the biogas into electric 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; Performing real-time processing and summarization of the energy flow data in the multi-energy flow system, comparing it with the energy demand, and uploading the comparison result to the cloud platform for management, to achieve digital management of multi-stage cascaded biogas energy.

2. The biogas energy multi-stage combined supply and digital energy management method according to claim 1, characterized in that, The specific decision-making process of the multi-dimensional parameter hierarchical decision tree includes: In the methane concentration shunt layer, obtaining the proportion of methane in the biogas. When the methane proportion is greater than a preset threshold, entering the high-quality biogas treatment path; when the methane proportion is less than the preset threshold, entering the low-quality biogas treatment path, where the preset threshold is 80%; In the volume analysis layer, obtaining the biogas volume. When the biogas volume is greater than a preset volume threshold, directly using the biogas as combustion-supporting air; when the biogas volume is less than the preset volume threshold, entering the temperature difference comparison layer, where the preset volume threshold is 100 m³ / h; In the temperature difference comparison layer, obtaining the biogas temperature and comparing it with the first temperature difference and the second temperature difference. When the biogas temperature is less than the first temperature difference, using the biogas as supplementary combustion-supporting air; when the biogas temperature is greater than the first temperature difference and less than the second temperature difference, mixing the biogas with steam and then burning; when the biogas temperature is greater than the second temperature difference, directly burning and utilizing the biogas through an efficient combustion channel; In the calorific value evaluation layer, when the difference between the biogas temperature and the second temperature difference is greater than a preset temperature difference threshold, obtaining the lower calorific value and the lower combustion calorific value of the biogas, and determining the final treatment method of the biogas according to the lower calorific value and the lower 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, wherein The specific processing process of the calorific value evaluation layer includes: Obtaining the lower calorific value and the lower combustion calorific value of the biogas; When the lower calorific value is less than a first calorific value threshold and the lower combustion calorific value is less than a second calorific value threshold, supplementing the biogas as combustion-supporting air to the biomass combustion-supporting air channel; When the lower calorific value is greater than the first calorific value threshold and the lower combustion calorific value is less than the second calorific value threshold, mixing the biogas with steam, burning it through the combustion calorific value channel, and then supplementing the burned gas to the steam channel of the biomass pulp tower through the superheated steam supply channel; When the lower calorific value is less than the first calorific value threshold and the lower combustion calorific value is greater than the second calorific value threshold, after mixing biogas with steam, it is burned through the combustion calorific value channel, and then through the superheated steam supply channel, the burned gas is supplemented into the steam channel of the biomass pulp tower; When the lower calorific value is greater than the first calorific value threshold and the lower combustion calorific value is greater than the second calorific value threshold, biogas is supplemented into the biomass combustion air channel as combustion-supporting air; Among them, the first calorific value threshold is 21000 kj / m³, and the second calorific value threshold is 24000 kj / m³.

4. The biogas energy multi-stage combined supply and digital energy management method according to claim 1, characterized in that, The calculation processes of the first temperature difference and the second temperature difference include: Obtain the temperature required for papermaking and the waste heat temperature before waste heat utilization in the papermaking workshop, match the temperature required for papermaking with the waste heat temperature before waste heat utilization, and obtain the first temperature difference; Obtain the temperature required for papermaking and the waste heat temperature after waste heat recovery in the papermaking workshop, match the temperature required for papermaking with the waste heat temperature after waste heat recovery, and obtain the second temperature difference; Among them, when the temperature difference is greater than zero, it means that energy is insufficient and energy needs to be supplemented; when the temperature difference is less than zero, it means that 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, characterized in that, The process of converting biogas into a multi-energy flow system includes: Obtain the steam temperature and steam pressure. When the steam pressure is greater than the preset pressure threshold and the steam temperature is greater than the preset temperature threshold, steam is supplemented into the steam pipeline of the biomass pulp tower. When the steam pressure is less than the preset pressure threshold or the steam temperature is less than the preset temperature threshold, the supply of steam to the steam pipeline is stopped; Among them, the preset pressure threshold is 3 bar, and the preset temperature threshold is 135 °C; Drive a steam turbine to generate electricity with 0.8 MPa of high-quality heat energy, and the power generation efficiency is 55%, generating 0.12 MPa of heat energy to supply steam; Use 0.3 MPa of medium-quality heat energy for chemicals in the pulping process and pulp dilution in the papermaking process; Use 50 - 70 °C of low-quality heat energy, adopt a low-pressure organic Rankine cycle, and use the heat energy of steam driven in the form of a heat pump to generate the heat of low-temperature hot water for use in the fiberboard pulping process.

6. The biogas energy multi-stage combined supply and digital energy management method according to claim 1, characterized in that The energy economy evaluation and distribution process based on the multi-energy flow system includes: Determine the thermal prices of co-supplied steam and purchased steam through the gas state parameters in the gas production pool and the waste heat temperature, according to the conversion relationship between waste heat and electricity price; Determine the heat price conversion ratio according to the ratio of the biogas calorific value in the gas production pool to the co-supplied steam calorific value; Determine the co-supplied ratio of co-supplied steam and purchased steam according to the ratio of the co-supplied steam calorific value to the steam calorific value required for waste heat co-supply; Multiply the co-supplied ratio by the thermal price to obtain the gas purchase price and the sales price; When the gas purchase price is higher than the sales price, sell the waste heat; When the gas purchase price is lower than the sales price, prepare steam from the waste heat and supply it through the heat network; When the gas purchase price is equal to the sales price, prepare steam from the waste heat and transport it through the steam pipeline.

7. The biogas energy multi-stage combined supply and digital energy management method according to claim 1, wherein The electric energy, cold energy, heat energy, steam energy, high-quality suction air, and low-quality suction wind energy generated in the multi-energy flow system are sequentially transmitted to the cold energy usage and heat energy usage demand ends of the papermaking equipment; A multi-energy connector is set in a multi-level cascade supplier to connect the output end and the input end of the multi-level cascade supplier, facilitating the input and output of multi-energy flows. The multi-energy flow system successively divides the energy flow into steam energy flow, pulping energy flow, pulping process energy flow, papermaking process energy flow, and fiber process energy flow. The steam energy flow drives a steam turbine generator by thermal energy, and the efficiency of steam turbine power generation is 55%. The steam thermal energy pressure after the steam turbine is 0.12 MPa. The pulping energy flow successively undergoes input processing of the steam energy flow and the chemical energy flow. The pulping process energy flow is used to process the pulping link. The papermaking process energy flow is used to process the papermaking link. 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, characterized in that, The biogas parameters include the biogas volume and the proportion of methane in the biogas. The steam parameters include calorific value, mass flow rate, steam temperature, and steam pressure. After going through three technological processes of pulping, fiber making, and papermaking, the raw materials of a paper-making enterprise produce biogas, and the content of CH4 in the biogas is between 45% and 50%. The monitoring range of the steam parameters includes: the temperature monitoring range is 0 - 300 °C, and the accuracy is ±1 °C. The pressure monitoring range is 0 - 5 MPa, and the accuracy is ±0.01 MPa. The flow rate is monitored by an ultrasonic flowmeter, and the accuracy is ±0.5%.

9. The biogas energy multi-stage combined supply and digital energy management method according to claim 1, wherein, The energy flow conversion relationship of the multi-energy flow system includes: In the papermaking process, the low-grade thermal energy of the pulping process, the steam thermal energy with an evaporation pressure of 0.3 MPa, the high-temperature steam with an evaporation pressure of 0.8 MPa in the papermaking process, and the high-temperature steam driving the steam turbine generator. After passing through the steam turbine, the output steam thermal energy pressure is 0.12 MPa. In the pulping process, the high-grade thermal energy of the fiber process, the high-temperature steam in the pulping process, and the high-temperature steam driving the steam turbine generator. After passing through the steam turbine, the output steam thermal energy pressure is 0.12 MPa. In the fiber process, the high-grade thermal energy of the pulping process, the high-temperature steam with an evaporation pressure of 0.8 MPa, and the high-temperature steam driving the steam turbine generator. After passing through the steam turbine, the output steam thermal energy pressure is 0.12 MPa. In the multi-energy flow system, valves are provided between the biomass pulp tower, the biogas production tank, the heat storage buffer tank, the steam pipeline of the biomass pulp tower, the steam heat network of the biomass pulp tower, and the heat network of steam combined supply, and the valves are controlled by a PLC controller.

10. Biogas energy multi-stage combined supply and digital energy management system, characterized in that, It includes: A distributed sensing network for obtaining biogas parameters, steam parameters, and waste heat temperature parameters generated in the pulping, fiber making, and papermaking technological processes of a paper-making enterprise. A multi-dimensional parameter decision processing unit for classifying biogas through a multi-dimensional parameter hierarchical decision tree based on the biogas parameters. The multi-dimensional parameter hierarchical decision tree includes a methane concentration shunt layer, a volume analysis layer, a temperature difference comparison layer, and a calorific value evaluation layer. A temperature matching calculation unit for calculating a first temperature difference and a second temperature difference according to the steam parameters and the waste heat temperature parameters, and forming a temperature matching relationship based on the first temperature difference and the second temperature difference. An energy path determination unit, configured to determine the energy utilization path of biogas based on the temperature matching relationship and the hierarchical processing result of the multi-dimensional parameter hierarchical decision tree, and convert biogas into electric energy, thermal energy, cold energy, steam energy, high-quality suction air, and low-quality suction air according to the energy utilization path, so as to form a multi-energy flow system; A multi-level cascade supplier, configured to transmit the energy flow in the multi-energy flow system, which is composed of multiple multi-level cascade suppliers. At the output end of the multi-level cascade supplier, cold energy utilization and thermal energy utilization are provided, and at the input end of the multi-level cascade supplier, cold energy input, thermal energy input, and steam are provided; A multi-stage valve network, including multiple valves arranged between a biomass pulp tower, a gas production tank, and a heat storage buffer tank, and the valves are controlled by a PLC controller; A digital management unit, configured to perform real-time processing and summarization of the energy flow data in the multi-energy flow system, compare it with the energy demand, and upload the comparison result to the cloud platform for management, so as to realize the digital management of the multi-stage cascade-supplied biogas energy.

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