Sludge medium-high temperature anaerobic digestion system with shallow geothermal energy coupled with solar energy

Abstract

The invention provides a sludge medium-high temperature anaerobic digestion system with shallow geothermal energy coupled with solar energy. The sludge medium-high temperature anaerobic digestion system comprises a solar water heater device, a buried pipe underground collection system, a heat pump unit and a medium-high temperature sludge anaerobic digestion system, the solar water heater device and the buried pipe underground collection system are both in heat conduction connection with one side of the heat pump unit and used for providing heat energy, and the other side of the heat pump unit is in heat conduction connection with the medium-high temperature sludge anaerobic digestion system and used for transmitting the heat energy to the medium-high temperature sludge anaerobic digestion system. In the sludge anaerobic digestion system, green clean renewable energy replaces traditional fossil energy to supply heat energy for sludge anaerobic digestion, the problems that pollutants are generated, a large amount of greenhouse gas is discharged and the like due to combustion of the traditional fossil energy are solved, meanwhile, the energy purchase cost is saved, boiler facilities are built, and the energy utilization rate is increased. And the utilization of land resources is maximized, so that relatively high environmental benefits and relatively high economic benefits are realized.

Description

Technical Field

[0001] The invention relates to the technical field of green clean energy development, and in particular to a sludge medium- and high-temperature anaerobic digestion system that couples shallow geothermal energy with solar energy. Background Art

[0002] In the 21st century, with the increase in urbanization rate, the construction scale of urban sewage treatment plants has also increased. In sewage treatment, if sludge anaerobic digestion is fully utilized, a large amount of methane can be produced. Such a large-scale production of clean green energy-methane can make up for part of the energy shortage, which is conducive to the orderly promotion of energy green and low-carbon transformation and the adjustment of energy structure as soon as possible. However, the anaerobic digestion process of medium (high) sludge with high methane production requires a large amount of heat and energy. If traditional energy is used for sludge anaerobic digestion, it will cause high energy consumption, high emissions, high investment and high pollution. Therefore, medium / high temperature sludge anaerobic digestion requires clean green renewable energy to replace traditional fossil energy to provide heat energy.

[0003] As a clean, green and renewable energy, shallow geothermal energy has the characteristics of wide distribution, large reserves, stability and sustainability. With the help of heat pump technology, it has been rapidly developed and its share in the energy structure has been continuously increased. At present, the ground-source heat pump with buried pipe is one of the main technical means to develop shallow geothermal energy. This technology buries high-density polyethylene pipes (buried pipes) in underground rock and soil layers, and uses the circulating fluid (water) in the pipe as a heat transfer medium to exchange heat with the surrounding rock and soil, and transfers the heat extracted from the rock and soil to the heat pump unit. The reverse Carnot principle of the heat pump unit is used to convert low-grade heat sources into high-grade heat sources. However, if only the ground-source heat pump technology of buried pipes is used to develop and utilize shallow geothermal energy as a single energy source to provide heat energy for medium (high) sludge anaerobic digestion for a long time, it is easy to cause cold accumulation in boreholes, affecting the heat exchange efficiency. With long-term accumulation, it is easy to cause insufficient energy supply and affect production. Solar energy is also a clean, green and renewable energy source. Solar water heaters can be used to absorb solar radiation heat energy to provide heat energy for sludge anaerobic digestion. However, solar energy is greatly affected by environmental factors. For example, in rainy weather or at night, solar radiation heat energy cannot be utilized, and a stable and sustainable input of heat energy cannot be maintained, which is not conducive to anaerobic digestion of sludge.

[0004] At present, relevant patents are mainly divided into four types;

[0005] 1) Single energy source to supply heat: This type of patent mainly uses a clean energy source such as solar energy, geothermal energy, etc. to provide heat energy for anaerobic digestion of sludge. This type of system has problems such as instability or unsustainability due to the characteristics of the energy source itself.

[0006] 2) Composite energy is used in other fields: This type of patent uses composite energy for domestic water, building heating and cooling, but solar energy cannot effectively serve the cooling needs in summer. At the same time, this type of patent is used for building heating and cooling, which is prone to uneven cold and heat loads in winter and summer, causing cold accumulation of underground rock and soil, affecting the operating efficiency of the system.

[0007] 3) Simplified patent system: This type of patent mainly involves the area of ​​composite energy collection, lacking energy enhancement and terminal energy supply areas; in particular, the system lacks the complementary characteristics of composite energy and the cascade and recycling utilization of energy and resources.

[0008] 4) Mechanization of patent system: This type of patent lacks the linkage and intelligence of energy collection area, energy enhancement and terminal reaction area. Each link lacks temperature sensors, liquid level sensors, etc. The system positive and negative feedback is not timely. At the same time, this type of patent lacks flexibility and accuracy in the temperature control of thermal energy supply, which easily causes waste of resources and energy and lacks efficiency. Summary of the invention

[0009] In view of the defects in the prior art, the object of the present invention is to provide a medium- and high-temperature anaerobic digestion system for sludge by coupling shallow geothermal energy with solar energy.

[0010] The medium-high temperature anaerobic digestion system of sludge by coupling shallow geothermal energy with solar energy provided by the present invention comprises a solar water heater device, an underground collection system of buried pipes, a heat pump unit and a medium-high temperature anaerobic digestion system of sludge;

[0011] The solar water heater device and the underground pipe underground collection system are both thermally connected to one side of the heat pump unit for providing thermal energy, and the other side of the heat pump unit is thermally connected to the medium-high temperature sludge anaerobic digestion system for transferring thermal energy to the medium-high temperature sludge anaerobic digestion system.

[0012] Preferably, the solar water heater device comprises a solar collector, a circulating medium outlet pipe, a heat exchange copper tube, a solar water collector tank and a circulating medium inlet pipe;

[0013] The solar collector is connected to the inlet of the circulating working medium outlet pipe, the outlet of the circulating working medium outlet pipe is located inside the solar heat collector tank, and is connected to the inlet of the circulating working medium inlet pipe through a heat exchange copper pipe, and the outlet of the circulating working medium inlet pipe is connected to the solar collector;

[0014] The solar water collection tank is connected to the heat pump unit through a first hot water outlet pipe and a first cold water inlet pipe, the inlet of the first hot water outlet pipe is connected to the solar water collection tank, and the outlet of the first hot water outlet pipe is connected to the inlet of the first cold water inlet pipe;

[0015] The outlet of the first cold water inlet pipe is connected to the solar water collection tank, and the outlet of the first hot water outlet pipe is connected to the inlet of the first cold water inlet pipe, forming a water source side heat exchange pipe section, which is used to achieve heat exchange with the heat pump unit.

[0016] Preferably, the underground pipe underground data collection system comprises an underground heat exchanger, and the underground heat exchanger is arranged in an underground rock and soil layer;

[0017] The underground heat exchanger is connected to the heat pump unit through a second hot water outlet pipe and a second cold water inlet pipe, the inlet of the second hot water outlet pipe is connected to the underground heat exchanger, and the outlet of the second hot water outlet pipe is connected to the inlet of the second cold water inlet pipe;

[0018] The outlet of the second cold water inlet pipe is connected to the underground heat exchanger, and the outlet of the second hot water outlet pipe is connected to the inlet of the second cold water inlet pipe, forming a water source side heat exchange pipe section, which is used to achieve heat exchange with the heat pump unit.

[0019] Preferably, a water source water measurement circulation component is provided between the solar water heater device, the underground pipe underground collection system and the heat pump unit;

[0020] The water source water circulation component includes a water source side water collector and a water source side water distributor, and the inlet of the water source side water collector is respectively connected to the outlet of the first hot water outlet pipe of the solar water heater device and the outlet of the second hot water outlet pipe of the underground pipe underground collection system;

[0021] A water source side heat exchange pipe section is formed between the outlet of the water source side water collector and the inlet of the water source side water distributor. The outlet of the water source side water distributor is respectively connected to the first cold water inlet pipe of the solar water heater device and the inlet of the second cold water inlet pipe of the underground collection system of the buried pipe.

[0022] Preferably, the water source water circulation component also includes a first softened water tank, and the first softened water tank is connected to the water source side heat exchange pipe section at the outlet of the water source side water collector.

[0023] Preferably, the medium-high temperature sludge anaerobic digestion system comprises a gas storage tank, a medium-high temperature sludge anaerobic reaction tank, a sludge pretreatment tank, a sludge heater, a sludge tank, a cold water outlet pipe and a hot water inlet pipe;

[0024] The gas storage tank is connected to the medium-high temperature sludge anaerobic reaction tank, the sludge pool is connected to the sludge heater, and the medium-high temperature sludge anaerobic reaction tank, the sludge pretreatment tank and the sludge heater are all connected to the inlet of the cold water outlet pipe;

[0025] The outlet of the cold water outlet pipe is connected to the inlet of the hot water inlet pipe to form a terminal heat exchange pipe section, and the outlet of the hot water inlet pipe is respectively connected to the medium and high temperature sludge anaerobic reaction tank, the sludge pretreatment tank and the sludge heater.

[0026] Preferably, a terminal water circulation component is provided between the heat pump unit and the medium-high temperature sludge anaerobic digestion system, and the terminal water circulation component includes a terminal water collector and a terminal water distributor;

[0027] The inlet of the terminal water collector is connected to the outlet of the cold water outlet pipe of the medium-high temperature sludge anaerobic digestion system, and a terminal heat exchange pipe section is formed between the outlet of the terminal water collector and the inlet of the terminal water distributor. The outlet of the terminal water distributor is connected to the inlet of the hot water inlet pipe of the medium-high temperature sludge anaerobic digestion system.

[0028] Preferably, the terminal water circulation assembly further includes a second softened water tank, and the second softened water tank is connected to the second heat exchange pipe at the outlet of the terminal water collector.

[0029] Preferably, the solar water heater device further comprises a collector temperature sensor, an automatic control device, a solar water tank temperature sensor, a solar water tank liquid level gauge, an expansion tank, an exhaust valve and a linkage control valve;

[0030] The collector temperature sensor is arranged on the solar collector, the solar water tank temperature sensor and the solar water tank liquid level meter are arranged inside the solar water collector tank, the exhaust valve is arranged on the top of the solar water collector tank, and the expansion tank is connected to the inlet of the circulating medium inlet pipe;

[0031] The linkage control valve is arranged on the circulating medium inlet pipe and the circulating medium outlet pipe, and the collector temperature sensor, the solar water tank temperature sensor, the solar water tank liquid level meter, and the linkage control valve are all connected with the automatic control device signal.

[0032] Preferably, the heat pump unit comprises an evaporator, a compressor, a condenser and an expansion valve connected end to end in sequence;

[0033] The evaporator is connected to the solar water heater device and the underground pipe underground collection system by heat conduction, and the condenser is connected to the medium-high temperature sludge anaerobic digestion system by heat conduction.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention realizes that in the sludge anaerobic digestion system, green, clean and renewable energy replaces traditional fossil energy to supply heat energy for sludge anaerobic digestion, avoiding the problems of pollutants generated by burning traditional fossil energy and the emission of a large amount of greenhouse gases. At the same time, it also saves energy purchase costs, builds boiler facilities, and maximizes the use of land resources, achieving both higher environmental benefits and higher economic benefits.

[0036] 2. The present invention couples shallow geothermal energy with solar energy to supply thermal energy, which solves the limitations of a single energy source and combines the advantages and characteristics of the two energy sources. It not only solves the cold accumulation phenomenon in the development and utilization of shallow geothermal energy, but also solves the instability of solar energy utilization affected by the environment and climate. At the same time, the excess thermal energy of solar energy is also used for rock and soil heat storage to achieve energy cascade utilization. In summary, the two complement each other and improve the efficiency, stability and sustainability of the system.

[0037] 3. The present invention couples shallow geothermal energy with solar energy and combines it with heat pump technology to supply heat energy for industrial production. The entire system uses temperature sensors, liquid level sensors, linkage control valves and other automatic control devices to achieve intelligent control, which can accurately control the efficient operation of the system. At the same time, the system's thermal energy conversion carrier water is closed and recycled. This patent neither consumes water resources nor causes energy loss, saving water resources and energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0039] Figure 1 It is a schematic diagram of the overall system of the present invention;

[0040] Figure 2 It is a structural schematic diagram of the solar water heater device in the present invention;

[0041] Figure 3 It is a structural schematic diagram of the underground pipe underground data collection system of the present invention;

[0042] Figure 4 It is a structural schematic diagram of the heat pump unit in the present invention;

[0043] Figure 5 It is a schematic diagram of the structure of the medium-high temperature sludge anaerobic digestion system of the present invention.

[0044] The figure shows:

[0045] Solar collector 1 Compressor 19

[0046] Collector temperature sensor 2 Second softening water tank 20

[0047] Circulating medium outlet pipe 3 End water collector 21

[0048] Automatic control device 4 End water distributor 22

[0049] Solar collector bracket 5 Gas tank 23

[0050] Solar water tank temperature sensor 6 Biogas flow meter 24

[0051] Expansion tank 7 Medium and high temperature sludge anaerobic reaction tank 25

[0052] Solar water tank level meter 8 Sludge pretreatment tank 26

[0053] Exhaust valve 9 Sludge heater 27

[0054] Heat exchange copper tube 10 Sludge tank 28

[0055] First hot water outlet pipe 11 water pump 29

[0056] Water source side water collector 12 Underground heat exchanger 30

[0057] First softened water tank 13 Underground rock layer 31

[0058] First cold water inlet pipe 14 Solar water collection tank 32

[0059] Water source side water distributor 15 drain valve 33

[0060] Evaporator 16 linkage control valve 34

[0061] Expansion valve 17 Filter device 35

[0062] Condenser 18 System Intelligent Control Panel 36 DETAILED DESCRIPTION

[0063] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0064] The present invention discloses a medium- and high-temperature anaerobic digestion system for sludge by coupling shallow geothermal energy with solar energy. It proposes coupling shallow geothermal energy with solar energy, and combining a heat pump unit to extract heat energy to supply anaerobic digestion reaction of sludge, so as to replace traditional fossil energy, and avoid the problem of pollutants produced by combustion of fossil energy and greenhouse gas emissions. On this basis, a device for coupling solar energy with shallow geothermal energy is designed and proposed, and an operation mode that complements each other is proposed. It is proposed to utilize the residual hot water of solar energy after extraction to carry out a shallow geothermal energy heat storage mode, and utilize the stability and sustainability of shallow geothermal energy to make up for the instability and unsustainability of solar energy.

[0065] Specifically, the present invention mainly couples shallow geothermal energy with solar energy and combines heat pump technology to provide heat energy for medium / high temperature sludge anaerobic digestion, such as Figure 1-4 As shown in the figure, it is mainly divided into four areas, namely solar water heater device, underground pipe collection system, heat pump unit and medium and high temperature sludge anaerobic digestion system. The solar water heater device and underground pipe collection system are energy collection areas, respectively as shown in the figure. Figure 2 and 3 As shown; the heat pump unit is the energy improvement area, such as Figure 4 As shown; the specific structure of the medium and high temperature sludge anaerobic digestion system is as follows Figure 5 In a preferred embodiment, the sludge medium-temperature anaerobic digestion system using shallow geothermal energy coupled with solar energy is connected to the system intelligent control console 36 to achieve intelligent control;

[0066] like Figure 1 As shown, the solar water heater device includes a solar collector 1, a circulating medium outlet pipe 3, a solar collector bracket 5, a heat exchange copper tube 10, a solar water collector tank 32, a circulating medium inlet pipe, a collector temperature sensor 2, an automatic control device 4, a solar water tank temperature sensor 6, a solar water tank liquid level meter 8, an expansion tank 7, an exhaust valve 9 and a linkage control valve 34;

[0067] The solar thermal collector 1 is connected to the inlet of the circulating working fluid outlet pipe 3, the outlet of the circulating working fluid outlet pipe 3 is located inside the solar heat collection tank 32, and is connected to the inlet of the circulating working fluid inlet pipe through the heat exchange copper tube 10, and the outlet of the circulating working fluid inlet pipe is connected to the solar thermal collector 1; the solar heat collection tank 32 is connected to the heat pump unit through the first hot water outlet pipe 11 and the first cold water inlet pipe 14, the inlet of the first hot water outlet pipe 11 is connected to the solar heat collection tank 32, and the outlet of the first hot water outlet pipe 11 is connected to the inlet of the first cold water inlet pipe 14; the outlet of the first cold water inlet pipe 14 is connected to the solar heat collection tank 32, and the outlet of the first hot water outlet pipe 11 is connected to the inlet of the first cold water inlet pipe 14, and a water source side heat exchange pipe section is formed, and the water source side heat exchange pipe section is used to realize heat exchange with the heat pump unit.

[0068] The collector temperature sensor 2 is arranged on the solar collector 1, the solar water tank temperature sensor 6 and the solar water tank liquid level meter 8 are both arranged inside the solar water collector tank 32, the exhaust valve 9 is arranged on the top of the solar water collector tank 32, and the expansion tank 7 is connected to the inlet of the circulating working fluid inlet pipe; the linkage control valve 34 is arranged on the circulating working fluid inlet pipe and the circulating working fluid outlet pipe 3, and the collector temperature sensor 2, the solar water tank temperature sensor 6, the solar water tank liquid level meter 8, and the linkage control valve 34 are all connected to the signal of the automatic control device 4.

[0069] The solar water heater device mainly utilizes the solar water collector to absorb solar radiation energy, and is suitable for sunny days with good sunshine. It mainly utilizes the circulating working fluid to absorb solar radiation heat energy through the solar thermal collector 1 (vacuum tube), enters the heat exchange copper tube 10 and exchanges heat with the cold water in the solar water collection tank 32 to increase the cold water temperature. The solar water tank temperature sensor 6, solar water tank level meter 8 and linkage control valve 34 in the solar water collection tank 32 are used in combination with the automatic control device 4 to adjust the water outlet temperature and flow of the solar water heater as needed, thereby achieving high efficiency and timeliness. The hot water of the solar water heater enters the water collector 12 on the water source side from the solar water collection tank 32, enters the heat pump unit under the action of the water pump 29, and exchanges heat with the circulating medium in the evaporator 16. The circulating water after heat exchange enters the water distributor 15 on the water source side again, and then enters the next cycle. At the same time, if the water temperature is relatively high (the water temperature is higher than the initial temperature of the rock and soil layer), it can also enter the underground pipe heat exchanger for circulation, discharge the heat into the rock and soil, store heat, and then the circulating water re-enters the solar water collection tank 32. This area can use a high borosilicate vacuum collector tube with an outer diameter of 70mm and a length of 1800mm, with a capacity of 4-5L (1m 2 8-10 vacuum collector tubes can be installed). According to experience, the ratio of storage tank capacity to collector tube number is 11:1. 44-55L of hot water can be supplied per square meter. The power of solar collector per square meter is between 0.4kW-0.9kW, and the outlet water temperature can reach 40℃-60℃. The comprehensive annual average power is 5kW / d. The solar water heater can be reasonably designed for installation according to the load of high-temperature anaerobic digestion system.

[0070] The underground collection system of buried pipes mainly uses the underground collection system of buried pipes to exchange heat with the surrounding rock and soil layers through circulating water. The circulating water after heat exchange exchanges heat with the circulating working fluid in the evaporator 16 of the heat pump unit, and is converted into high-temperature and high-pressure gas after the compressor 19. It releases heat energy in the condenser 18 tube and exchanges heat with the water outside the condenser 18 to increase its temperature. The heat carrier-water enters the terminal water distributor 22. The shallow geothermal energy is used underground in this area. The shallow geothermal energy uses DN32 high-density polyethylene pipes (PE pipes) with a thermal conductivity of 0.4-0.7W / mk. The burial depth is 80-120m deep. The backfill material adopts the optimal ratio of water: cement: quartz sand: high-efficiency water reducer: expansion agent: bentonite

[0071] =0.55:1:2:0.014:0.06:0.01, the backfill material can ensure good thermal conductivity, as well as fluidity and expansion of the backfill material. Its thermal conductivity can reach 2.87w / (mk). The underground buried pipe group adopts parallel form, the borehole spacing is between 3-6 meters, the inlet and outlet water temperature difference is designed to be below 5℃, and the power of each borehole is about 5-8kW according to experience. The design load should meet the normal operation of sludge anaerobic digestion. The solar water heaters and underground pipe heat exchanger pipelines in zones 1 and 2 are connected in parallel and then collected in the water collector. The design loads of the two must be guaranteed, and the operation of a single heat source can meet the heat energy required for sludge anaerobic digestion reaction.

[0072] The heat pump unit is mainly an energy boosting area, that is, a heat pump unit area. This area mainly uses the reverse Carnot cycle principle to extract shallow geothermal energy and solar energy from circulating water. The low-temperature and low-pressure circulating working fluid in the evaporator 16 absorbs heat through evaporation, extracts the heat energy in the circulating water, and turns it into a low-temperature and low-pressure gas. It enters the compressor 19. After the compressor 19 does work, the circulating working fluid becomes a high-temperature and high-pressure gas, and enters the condenser 18 again. It exchanges heat with the circulating water passing through the outside of the tube, transfers heat to the terminal circulating water, and the circulating working fluid becomes a low-temperature and high-pressure liquid. It enters the expansion valve 17, and after throttling the expansion valve 17, it becomes a low-temperature and low-pressure liquid and enters the evaporator 16 for recirculation. In this area, the reverse Carnot principle is used to extract heat energy from the low-temperature liquid to produce medium / high-temperature liquid, and the temperature can be 65°C or even higher, where different temperatures are set according to production needs. Using heat pump technology, the heat pump unit uses a screw dual compressor heat pump unit to extract heat energy to meet the requirements of medium / high temperature sludge anaerobic digestion reaction at the same time. When selecting the heating power of the heat pump unit, the safety factor is guaranteed to be 1.1-1.2. Among them, the outlet water temperature of the solar water heater can reach 40-60℃ during the day. At night or when solar energy is insufficient, shallow geothermal energy can use water circulation and rock and soil heat exchange to extract a temperature difference of 5℃, and it is sustainable. Using heat pump technology, the temperature difference of solar water outlet can be extracted by more than 20℃, and hot water below 85℃ can be produced with an energy efficiency ratio of more than 3.5 (if used for high temperature sludge anaerobic digestion, a dual compressor unit can be used. The unit uses solar water outlet for energy supply, and the COP can reach more than 3.5. If shallow geothermal energy is used, the water outlet COP is relatively low at about 2.5), which has a certain degree of high efficiency. The operation strategy of the heat pump unit should give priority to the use of solar water heaters for energy supply. Under the premise of meeting the production load, the temperature of the solar hot water after extracting heat energy should be kept higher than the initial low temperature of the underground rock and soil, and used for underground rock heat storage.

[0073] The medium / high temperature sludge anaerobic digestion system is a medium / high temperature sludge anaerobic digestion area, which mainly consists of a sludge pool 28, a sludge heater 27, a sludge pretreatment tank 26 and a medium / high temperature sludge anaerobic reaction tank 25. This area transports the sludge with a water content of 80% in the sludge pool 28 to the sludge heater 27, uses the effluent from the heat pump system to heat the sludge to a certain temperature, and enters the sludge pretreatment tank 26 to balance the peak load of the incoming sludge. According to the anaerobic digestion process in the medium / high temperature sludge anaerobic reaction tank 25, the incoming sludge volume is reasonably regulated, and the sludge in the sludge pretreatment tank 26 is transported to the medium / high temperature sludge anaerobic reaction tank 25 for reaction to produce biogas, and the produced biogas enters the gas storage tank 23. Preferably, a biogas flowmeter 24 is provided between the gas storage tank 23 and the medium-high temperature sludge anaerobic reaction tank 25, and a drain valve 33 is provided at the bottom of the medium-high temperature sludge anaerobic reaction tank 25. The working medium after heat exchange passes through the terminal water collector 21 and enters the heat pump unit for heat exchange, wherein a filter device 35 is provided at the inlet of the terminal water collector 21;

[0074] The shallow geothermal energy coupled with solar energy medium / high temperature anaerobic digestion system of the present invention couples two clean energies, shallow geothermal energy and solar energy, and generates medium / high temperature liquid through a heat pump unit for medium / high temperature anaerobic digestion of sludge. The entire process only uses clean green energy to supply heat energy, thereby realizing green and low-carbon production.

[0075] The operation of the medium / high temperature anaerobic digestion system of sludge by coupling shallow geothermal energy with solar energy of the present invention is mainly divided into three links and the specific measures are as follows:

[0076] 1) Energy collection

[0077] During the anaerobic digestion of sludge, the energy collection area can realize three modes: 1) During the day (when the sunlight is good), the automatic control device is used to turn on the solar water heater, close the hot water outlet valve of the underground pipe underground collection system, and the circulating medium in the solar water collection tank is turned on and enters the vacuum tube of the solar collector to absorb solar radiation heat energy, increase the temperature, evaporate into gas, and enter the heat exchange copper tube of the solar water collection tank to exchange heat with the cold water entering the water tank. As the water temperature rises and reaches the set temperature, the hot water outlet valve of the solar water collection tank is opened, the water pump starts to run, and the hot water enters the water source side collector. The water source side collector filled with hot water opens the valve and enters the heat pump unit under the action of the water pump to exchange heat with the circulating medium in the evaporator. The water temperature drops rapidly and enters the water distributor on the water source side. According to the water temperature of the water distributor, if the water temperature in the water distributor is relatively high and higher than the initial temperature of the underground rock and soil, open the water inlet valve and water pump of the buried pipe geothermal collection system at this time, and let the hot water in the water distributor enter the PE pipe to dissipate heat to the surrounding rock and soil layers to achieve the effect of storing heat energy. The water after heat discharge enters the solar water collection tank under the action of the water pump and starts to circulate again. 2) If there is no sunlight during the day or at night, turn off the solar water heater device, open the valve and water pump of the buried pipe geothermal energy collection system, and the circulating water in the PE pipe starts to circulate and exchange heat with the surrounding rock and soil. The circulating water after heat exchange enters the water collector on the water source side, and then exchanges heat with the circulating working fluid in the evaporator of the heat pump unit. The circulating water after heat exchange enters the water distributor on the water source side to start the next cycle. 3) If the solar radiation energy is low during the day and cannot meet the heat energy demand of anaerobic digestion of sludge, the underground geothermal energy collection system and the solar collector will be turned on and the two will operate together. At this time, the automatic control device will adjust the outlet water temperature and flow of the solar water heater according to the demand for industrial production heat energy and the circulating water temperature in the PE pipe to meet the optimal energy efficiency and achieve efficient energy utilization. After the heat exchange between the two, the circulating water enters the water collector on the water source side, and then enters the heat pump unit and the circulating working fluid in the evaporator for heat exchange. After the heat exchange, the cooling water enters the water distributor and starts the circulation operation again.

[0078] 2) Energy boosting session

[0079] The hot water in the water collector on the water source side exchanges heat with the circulating working fluid in the evaporator. The circulating working fluid absorbs heat through evaporation, extracts the heat energy in the circulating water, and becomes a low-temperature, low-pressure gas. It enters the compressor, and through compression, it does work. The circulating working fluid becomes a high-temperature, high-pressure gas, and enters the condenser again. It exchanges heat with the circulating water passing through the outside of the tube, and transfers the heat to the end circulating water. The circulating working fluid becomes a low-temperature, high-pressure liquid, enters the expansion valve, and after throttling by the expansion valve, it becomes a low-temperature, low-pressure liquid and enters the evaporator for recirculation. During this period, according to the temperature requirements of anaerobic digestion of sludge, the heat pump unit control system can be used to control and set the outlet water temperature. The outlet water temperature is adjustable (30℃-65℃, and the outlet water temperature can be further increased according to actual needs)

[0080] 3) Anaerobic digestion of terminal sludge

[0081] The circulating water after heat exchange enters the terminal water distributor. The hot water in the terminal water distributor is mainly transported to the sludge heater, the sludge pretreatment tank and the medium / high temperature sludge anaerobic reaction tank to maintain the required temperature for anaerobic digestion of sludge. The anaerobic digestion reaction process of sludge can be divided into the reaction start-up stage of microbial acclimation and the digestion operation stage of biogas production. Among them, the reaction start-up stage requires the temperature to change from low to high, and the digestion operation stage requires the temperature to be stable. The heat requirements of the two stages are different, especially the heat supply requirements in the reaction start-up stage are dynamically changed. At this time, the heat pump unit implements a dynamic control strategy for variable working conditions according to the actual reaction, and gradually increases the temperature. When the heat pump meets the required temperature in the startup stage, the heat pump outlet water temperature can be adjusted according to the biogas production stage to provide it with a stable and sustainable heating environment. In the whole process, the heated hot water passes through the water pump through the filter device and enters the water collector for circulating heat exchange.

[0082] Embodiment 1:

[0083] In order to further verify the feasibility of the scheme, the present invention takes the medium-temperature anaerobic digestion of sludge as a model, and the preliminary design of the scheme is as follows:

[0084] Taking 100 tons / day of sludge with a moisture content of 80% for medium-temperature anaerobic digestion as an example, the heat energy mainly involves water heating, dry sludge heating, heat exchange between the digester and the surrounding environment, and process heat loss. The required calorific value is calculated as 9.2325GJ / d according to the following method.

[0085] Q s =(T2-T1)×C S ×Q DS ×10 -3 (1)

[0086] Where: Q s—Heat required for sludge solid temperature increase, GJ; T1—initial temperature of dewatered sludge (20°C); T2—drying temperature (35°C); C S —Specific heat capacity of sludge, 3.62KJ / (kg·℃); Q DS —Dry sludge mass, kg.

[0087] Q W =C w ×Q W ×(T2-T1)×10 -6 (2)

[0088] Where: Q w —Heat absorbed by water in sludge, GJ; C w —Specific heat capacity of water, 4.2 kJ / (kg.℃); Q w —Mass of water, kg.

[0089]

[0090] In the formula: S1 is the total heat energy required, kg / d; а2 is the heat dissipation and heat exchange efficiency coefficient of the digester.

[0091] The solar collector power of a solar water heater can be expressed by the formula:

[0092] P=a×A×G×n (4)

[0093] Where P is the power of the collector tube, in W / m 2 ; a is the absorptivity of the collector, usually between 0.85-0.95; A is the surface area of ​​the collector, in m 2 ; G is the solar radiation intensity, unit is W / m; n is the thermal collection efficiency, generally between 0.5-0.8.

[0094] The actual power of solar water heaters is greatly affected by factors such as regionality, light intensity, material and installation angle. According to the empirical value of 1m 2 The heat generating power of the collector tube is about 500-1000W. According to the empirical value, the heat generating power is 5kWh / (m 2 .d) If solar water heaters are used completely, only 500 square meters of collector tubes are needed.

[0095] According to the development of shallow geothermal energy by buried pipe ground source heat pump, the relevant parameters of the buried pipe ground source heat pump collection system are designed with reference to geological conditions, hydrogeological conditions, etc. According to the economy and energy efficiency of buried pipe drilling, the most common drilling depth is currently 80-120 meters. Double U-shaped PE pipes are used as underground heat exchangers. The drilling power is estimated to be 5-8kW based on experience (except for extremely cold areas and areas with poor geothermal resources). This patent selects the above parameters as the basic data for calculation. According to the thermal energy power required for the medium-temperature sludge anaerobic digestion reaction of 106.87kW, according to the buried pipe design specifications and design safety factors, it can be seen that 16-26 boreholes can be drilled. The distance between boreholes is generally 3-6 meters. This article selects 4.5 meters, which means that approximately 1017-1653m is required. 2 The venue will suffice.

[0096] Based on the solar collector area of ​​500m 2 and underground pipe ground source heat pump area 1017m 2 -1653m 2 , it is possible to implement solar water heater devices on the ground and buried pipe collection systems underground, so as to utilize land resources spatially and improve the utilization rate of land resources.

[0097] The shallow geothermal energy coupled with solar energy medium / high temperature anaerobic digestion system provided in this embodiment extracts the heat energy of shallow geothermal energy and solar energy, two clean green energy sources, to replace traditional fossil energy. The two energy sources can replace fossil energy, which can save 276.1m3 of sludge anaerobic digestion system with a daily processing capacity of 100 tons and a water content of 80%. 3 / d natural gas, reducing 596.4kg / d of carbon dioxide emissions. Therefore, by using clean green energy to carry out industrial production, the entire process is pollution-free, green and low-carbon, solving the environmental problems and limiting factors caused by the general medium / high temperature sludge anaerobic digestion reaction production. At the same time, the patent uses shallow geothermal energy and solar energy to replace traditional fossil energy to supply heat energy, consuming only a small amount of electricity, without increasing the investment in purchasing traditional energy. According to the Beijing natural gas price of 0.33 yuan / m 3 Calculation shows that using this system to carry out anaerobic digestion of 1 ton of sludge with a moisture content of 80% can reduce the operating cost by 9.11 yuan. Therefore, the system reduces its high operating costs, improves its economy, and further promotes the development of medium / high temperature anaerobic digestion systems for sludge.

[0098] This embodiment utilizes the high efficiency of solar energy and the stability and sustainability of shallow geothermal energy, combines the two, complements each other, and solves the limitations of a single clean green energy source. In this patent, the design load of the solar water heater is equal to the design load of shallow geothermal energy, that is, a single heat source can meet the heat energy demand of the anaerobic digestion reaction of sludge. The operating strategy principle of the two is to give priority to the use of solar water heaters for energy supply, complement each other, and make full use of the large reserves and high stability of shallow geothermal energy. The characteristics make up for the situation when the solar water heater cannot supply energy due to the influence of climate, achieve auxiliary functions, continuously and stably supply heat energy, and maintain the stability of the system. On this basis, combined with heat pump technology, the supply temperature can be flexibly adjusted to achieve the stability, sustainability and efficiency of heat supply and intelligent control performance.

[0099] The system in this embodiment couples solar energy with shallow geothermal energy. During the day, solar water heaters can be used to absorb solar radiation and quickly raise the water temperature. The outlet water temperature of the water heater reaches above 45°C in winter and above 60°C in summer. By using heat pump technology, a temperature difference of more than 20°C in the water can be extracted to supply heat energy for anaerobic digestion of sludge. At this time, the operation of the buried pipe ground source heat pump can be stopped to give the underground rock and soil temperature effective recovery time. At the same time, the water temperature after heat exchange also has a certain amount of heat energy (the remaining water temperature is between 20-30°C, which is higher than the initial temperature of the underground rock and soil (generally, the initial temperature of the shallow rock and soil layer below 200 meters is lower than 20°C)). The return water higher than the initial ground temperature of the rock and soil can be used to start the underground rock and soil heat storage mode, store excess heat energy in the underground rock and soil, increase the temperature of the underground rock and soil layer, solve the cold accumulation phenomenon, and realize the cascade utilization of clean energy.

[0100] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0101] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A medium- and high-temperature anaerobic digestion system for sludge using shallow geothermal energy coupled with solar energy, characterized in that: It includes solar water heater devices, underground pipe underground collection systems, heat pump units, and medium- and high-temperature sludge anaerobic digestion systems; The solar water heater device and the underground pipe underground collection system are both thermally connected to one side of the heat pump unit for providing thermal energy, and the other side of the heat pump unit is thermally connected to the medium-high temperature sludge anaerobic digestion system for transferring thermal energy to the medium-high temperature sludge anaerobic digestion system.

2. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 1 is characterized in that: The solar water heater device comprises a solar heat collector (1), a circulating medium outlet pipe (3), a heat exchange copper pipe (10), a solar heat collector tank (32) and a circulating medium inlet pipe; The solar thermal collector (1) is connected to the inlet of a circulating working fluid outlet pipe (3), the outlet of the circulating working fluid outlet pipe (3) is located inside the solar thermal water collection tank (32), and is connected to the inlet of the circulating working fluid inlet pipe via a heat exchange copper pipe (10), and the outlet of the circulating working fluid inlet pipe is connected to the solar thermal collector (1); The solar water collection tank (32) is connected to the heat pump unit via a first hot water outlet pipe (11) and a first cold water inlet pipe (14); the inlet of the first hot water outlet pipe (11) is in communication with the solar water collection tank (32); and the outlet of the first hot water outlet pipe (11) is connected to the inlet of the first cold water inlet pipe (14); The outlet of the first cold water inlet pipe (14) is connected to the solar water collection tank (32), and the outlet of the first hot water outlet pipe (11) is connected to the inlet of the first cold water inlet pipe (14), thereby forming a water source side heat exchange pipe section, and the water source side heat exchange pipe section is used to achieve heat exchange with the heat pump unit.

3. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 1 is characterized in that: The underground pipe underground data collection system comprises an underground heat exchanger (30), wherein the underground heat exchanger (30) is arranged in an underground rock and soil layer (31); The underground heat exchanger (30) is connected to the heat pump unit via a second hot water outlet pipe and a second cold water inlet pipe, the inlet of the second hot water outlet pipe is in communication with the underground heat exchanger (30), and the outlet of the second hot water outlet pipe is connected to the inlet of the second cold water inlet pipe; The outlet of the second cold water inlet pipe is connected to the underground heat exchanger (30), and the outlet of the second hot water outlet pipe is connected to the inlet of the second cold water inlet pipe, forming a water source side heat exchange pipe section, which is used to achieve heat exchange with the heat pump unit.

4. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 1 is characterized in that: A water source water measurement circulation component is provided between the solar water heater device, the underground pipe underground collection system and the heat pump unit; The water source water circulation component comprises a water source side water collector (12) and a water source side water distributor (15), wherein the inlet of the water source side water collector (12) is respectively connected to the outlet of the first hot water outlet pipe (11) of the solar water heater device and the outlet of the second hot water outlet pipe of the underground pipe underground collection system; A water source side heat exchange pipe section is formed between the outlet of the water source side water collector (12) and the inlet of the water source side water distributor (15), and the outlet of the water source side water distributor (15) is respectively connected to the inlet of the first cold water inlet pipe (14) of the solar water heater device and the second cold water inlet pipe of the underground pipe underground collection system.

5. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 4 is characterized in that: The water source water circulation component further comprises a first softened water tank (13), wherein the first softened water tank (13) is connected to the water source heat exchange pipe section at the outlet of the water source side water collector (12).

6. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 1, characterized in that: The medium-high temperature sludge anaerobic digestion system comprises a gas storage tank (23), a medium-high temperature sludge anaerobic reaction tank (25), a sludge pretreatment tank (26), a sludge heater (27), a sludge pool (28), a cold water outlet pipe and a hot water inlet pipe; The gas storage tank (23) is connected to the medium-high temperature sludge anaerobic reaction tank (25), the sludge pool (28) is connected to the sludge heater (27), and the medium-high temperature sludge anaerobic reaction tank (25), the sludge pretreatment tank (26) and the sludge heater (27) are all connected to the inlet of the cold water outlet pipe; The outlet of the cold water outlet pipe is connected to the inlet of the hot water inlet pipe to form a terminal heat exchange pipe section, and the outlet of the hot water inlet pipe is respectively connected to the medium and high temperature sludge anaerobic reaction tank (25), the sludge pretreatment tank (26) and the sludge heater (27).

7. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 1 is characterized in that: A terminal water circulation component is arranged between the heat pump unit and the medium-high temperature sludge anaerobic digestion system, and the terminal water circulation component comprises a terminal water collector (21) and a terminal water distributor (22); The inlet of the terminal water collector (21) is connected to the outlet of the cold water outlet pipe of the medium-high temperature sludge anaerobic digestion system, and a terminal heat exchange pipe section is formed between the outlet of the terminal water collector (21) and the inlet of the terminal water distributor (22), and the outlet of the terminal water distributor (22) is connected to the inlet of the hot water inlet pipe of the medium-high temperature sludge anaerobic digestion system.

8. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 7, characterized in that: The terminal water circulation assembly further comprises a second softened water tank (20), wherein the second softened water tank (20) is connected to a second heat exchange pipe at the outlet of the terminal water collector (21).

9. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 2, characterized in that: The solar water heater device also includes a collector temperature sensor (2), an automatic control device (4), a solar water tank temperature sensor (6), a solar water tank liquid level meter (8), an expansion tank (7), an exhaust valve (9) and a linkage control valve (34); The collector temperature sensor (2) is arranged on the solar collector (1), the solar water tank temperature sensor (6) and the solar water tank liquid level sensor (8) are both arranged inside the solar water collection tank (32), the exhaust valve (9) is arranged on the top of the solar water collection tank (32), and the expansion tank (7) is connected to the inlet of the circulating medium inlet pipe; The linkage control valve (34) is arranged on the circulating medium inlet pipe and the circulating medium outlet pipe (3); the collector temperature sensor (2), the solar water tank temperature sensor (6), the solar water tank liquid level sensor (8), and the linkage control valve (34) are all connected to the automatic control device (4) by signal.

10. The medium- and high-temperature anaerobic digestion system of sludge using shallow geothermal energy coupled with solar energy according to claim 1, characterized in that: The heat pump unit comprises an evaporator (16), a compressor (19), a condenser (18) and an expansion valve (17) which are connected end to end in sequence; The evaporator (16) is connected to the solar water heater device and the underground pipe collection system by heat conduction, and the condenser (18) is connected to the medium-high temperature sludge anaerobic digestion system by heat conduction.

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