Heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery

Abstract

The heat pump-deaerator integrated energy-saving system based on waste heat recovery of steam boiler flue gas of the present invention is that the high-temperature flue gas sent from the boiler enters the economizer and exchanges heat with the water sent by the deaerator. After the low-temperature flue gas exchanges heat with the water from the normal-temperature water tank, the flue gas enters the evaporator in the heat pump and exchanges heat with the refrigerant working medium to reduce the flue gas temperature; the water in the normal-temperature water tank exchanges heat with the low-temperature flue gas in the boiler condensing device, and after rising to a first target temperature, forms preheated water, which enters the heating water tank for storage. The preheated water enters the condenser and exchanges heat with the refrigerant working medium to raise the water temperature. After being heated to a second target temperature, it is deoxygenated and then transported to the boiler for heating to generate steam; this solution innovatively couples the heat pump and the deaerator, recovers the waste heat of the flue gas and the deaerator, increases the deaerator inlet water temperature, reduces the steam energy consumption of the deaerator, increases the steam supply of the steam boiler, and realizes the cascade utilization of waste heat and the synergistic efficiency of the heat pump.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat pump equipment, and in particular relates to a heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery. Background Art

[0002] With the increase in industrial production and energy consumption, boiler systems generate significant amounts of waste heat during operation, particularly in flue gas. Failure to effectively recover this waste heat not only wastes energy but also increases the environmental burden. The efficiency and operational performance of traditional waste heat recovery technologies are limited by factors such as flue gas temperature and heat exchange efficiency. To further improve the thermal efficiency of boiler systems, reduce energy consumption, and reduce environmental pollution, developing more efficient waste heat recovery technologies is crucial.

[0003] Flue gas source heat pumps, a technology that efficiently recovers waste heat from exhaust gas and heats hot water, have garnered increasing attention in recent years. By optimizing the utilization of flue gas heat sources, flue gas source heat pump systems can improve the overall operating efficiency of boiler systems. However, existing technologies are generally less than ideal for recovering waste heat from flue gas, with much of the heat being wasted. This not only increases energy consumption but also worsens environmental pollution.

[0004] The current mainstream technology primarily combines gas turbines and waste heat boilers to achieve a combined supply of electricity and heat. When burning fuels such as natural gas, the gas turbine first drives a generator to generate electricity. The waste heat boiler, on the other hand, recovers heat from the gas turbine's exhaust to heat water or steam for the city's centralized heating system. This approach allows for comprehensive energy utilization, but it still presents some challenges. Existing technology primarily combines gas turbines and waste heat boilers. While this approach achieves comprehensive energy utilization, it comes with high equipment costs, difficult maintenance, and high operating costs. A Chinese patent with publication number CN115095897B, entitled "Gas Turbine Combined Flash Heat Pump Distributed Combined Cooling, Heating and Power System," discloses a gas turbine combined flash heat pump distributed combined cooling, heating and power system. The system includes a user heating return pipe, a user heating water supply pipe, a waste heat boiler, a shell and tube heat exchanger, a generator, a condenser, an absorber, an evaporator, a condensate pump, a vacuum pump, a condensate tank, a flue gas heat exchanger, a heat network circulating water pump, and a cooling tower. The system utilizes the flue gas from the gas turbine in a cascaded manner to produce steam and hot water. This system is combined with an absorption heat pump for cooling or heating, and a sewage negative pressure flash evaporation system is established. While recovering low-grade waste heat from domestic sewage, the system improves the COP of the heat pump, reduces steam consumption, further reduces energy supply costs, improves energy utilization, and enhances energy supply quality, achieving the goals of energy conservation and emission reduction. A Chinese patent, published with publication number CN116592336A and titled "A Self-Coupling Utilization System for Low-Grade Waste Heat from a Gas-Steam Boiler," discloses a self-coupling utilization system for low-grade waste heat from a gas-steam boiler. The system comprises a water tank, a flue gas energy-saving heat exchanger, a deaerator, an electric heat pump, a gas-steam boiler, and a spray heat exchanger. The water tank is used to inject softened water into the system. The exhaust gas from the gas-steam boiler sequentially heats the softened water and intermediate water. The heated softened water enters the deaerator and then the gas-steam boiler's feedwater system. The intermediate water is heated by heat exchange in a spray heat exchanger, then flows through the intermediate water pipeline into the electric heat pump unit to release heat and cool down. Overall, the above solution still has room for improvement in terms of cascaded flue gas utilization and improved energy efficiency. Summary of the Invention

[0005] The object of the present invention is to provide a heat pump-deaerator integrated energy-saving system capable of recovering waste heat in boiler flue gas and waste gas from a deaerator.

[0006] In order to solve the above technical problems, the present invention discloses a heat pump-deaerator integrated energy-saving system based on the recovery of waste heat from the flue gas of a steam boiler. The system combines a flue gas source heat pump with an evaporator and a condenser to recover the waste heat in the flue gas generated by the boiler to reduce pollution and improve energy utilization. The system comprises: a heat pump unit, a heat exchange unit and a water storage unit. The heat pump unit is connected to the flue gas outlet of the boiler. The heat pump unit comprises an evaporator and a condenser. The heat exchange unit comprises an economizer and a boiler condensing device. The water storage unit comprises at least a normal temperature water tank and a heating water tank. The high-temperature flue gas sent from the boiler enters the economizer and exchanges heat with the water sent from the deaerator. The high-temperature flue gas The temperature is lowered to low-temperature flue gas, which enters the boiler condensing device for heat exchange with water from the normal-temperature water tank. Part or all of the flue gas then enters the evaporator in the heat pump for heat exchange with the refrigerant to lower the flue gas temperature, and is finally discharged through the flue. The water in the normal-temperature water tank exchanges heat with the low-temperature flue gas in the boiler condensing device, and forms preheated water after rising to the first target temperature. The preheated water enters the heating water tank for storage, and the preheated water enters the condenser of the heat pump unit for heat exchange with the refrigerant to increase the water temperature. After being heated to the second target temperature, high-temperature water is formed. The high-temperature water flows through the deaerator for deoxygenation, and is then transported to the boiler for heating to generate steam.

[0007] Preferably, through intelligent control of the system, the water in the normal temperature water tank is driven by a water pump and circulates in the boiler condensing device to exchange heat with the low-temperature flue gas until it is discharged from the normal temperature water tank after rising to the first target temperature, and then normal temperature water is injected into the normal temperature water tank; the preheated water is driven by a water pump and circulates in the condenser to exchange heat with the refrigerant working medium to achieve further increase in water temperature until it is raised to the second target temperature.

[0008] Preferably, the first target temperature is 40-50°C, and the second target temperature is 70-90°C.

[0009] Preferably, the heating water tank includes a water tank to be heated and a high-temperature water tank; the water tank to be heated is used to temporarily store water reaching the first target temperature flowing out of the normal-temperature water tank, and the high-temperature water tank is used to temporarily store water reaching the second target temperature flowing out of the water tank to be heated.

[0010] Preferably, the water tank to be heated is connected to the condenser of the heat pump unit. The preheated water in the water tank to be heated is driven by the water pump and circulated in the condenser to exchange heat with the refrigerant, thereby raising the temperature of the preheated water to the second target temperature.

[0011] Preferably, after the preheated water in the water tank to be heated is heated to the second target temperature, it flows into the high-temperature water tank for temporary storage, and then the preheated water is injected into the water tank to be heated.

[0012] Preferably, the high-temperature water tank is connected to the economizer, and the high-temperature water flowing out of the high-temperature water tank is deoxygenated by the deaerator, and then is finally heated by the economizer and the high-temperature flue gas before being transported to the boiler.

[0013] Preferably, the water tanks to be heated include several water tanks arranged in parallel with the condensers of the heat pump units.

[0014] Preferably, the water tank to be heated is connected to the heat pump unit condenser through an electrically controlled valve, and only one heating water tank is connected to the heat pump unit condenser for heating at the same time.

[0015] Preferably, the exhaust gas from the deaerator is mixed with the low-temperature flue gas before entering the heat pump unit, thereby recovering and utilizing the waste heat in the exhaust gas from the deaerator.

[0016] The heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery of the present invention is designed to achieve efficient and stable operation of the equipment by coupling the heat pump and deaerator, combining intelligent control and innovative design, and has at least the following advantages:

[0017] 1. The innovative coupling of the heat pump and deaerator recovers waste heat from flue gas and the deaerator to increase the deaerator inlet water temperature, reduce the deaerator steam energy consumption, increase the steam supply to the steam boiler, achieve energy savings of 4-8%, optimize system energy efficiency, and realize cascade utilization of waste heat and synergistic efficiency of the heat pump.

[0018] 2. Normal temperature water and preheated water are circulated and heated under the promotion of water pump, so that the heat pump system adopts small flow and large temperature difference on the water side, which can achieve an inlet and outlet water temperature difference of 20-30℃, solving the large temperature difference heating of water caused by heat pump application of steam boiler.

[0019] 3. Due to the innovative design and intelligent control of the system's thermal cycle, the flow is intelligently adjusted through the on-off valve, wind speed valve and circulating fan to dynamically adjust the flow. When the water outlet of the heat pump system is 80°C, the COP (heating performance coefficient) is greater than 3.5, which is more than 20% higher than the market average. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery.

[0021] The blue dotted line shows the flow direction of water, and the pink dotted line shows the flow direction of gas.

[0022] The numbers in the figure are: boiler 1, economizer 2, boiler condensing device 3, water pump 4, normal temperature water tank 5, heating water tank 6, switch valve 7, deaerator 8, air duct valve 9, fan 10, evaporator 11, compressor 12, condenser 13, expansion valve 14. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below through examples so that those skilled in the art can implement the invention with reference to the description.

[0024] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0025] A heat pump-deaerator 8 integrated energy-saving system based on steam boiler flue gas waste heat recovery, which recovers and utilizes the waste heat in the flue gas generated by the boiler 1 through a flue gas source heat pump combined with an evaporator 11 and a condenser 13 to reduce pollution and improve energy utilization. The system includes: a heat pump unit, a heat exchange unit and a water storage unit. The heat pump unit is connected to the flue gas outlet of the boiler. The heat pump unit includes an evaporator 11 and a condenser 13. The evaporator 11 and the condenser 13 realize an evaporation-compression cycle through a compressor 12 and an expansion valve 14.

[0026] The heat exchange unit includes an economizer 2 and a boiler condensing device 3, and the water storage unit includes at least a normal temperature water tank 5 and a heating water tank 6; the high-temperature flue gas sent from the boiler 1 enters the economizer 2 and performs heat exchange with the water sent from the deaerator 8, and the high-temperature flue gas is cooled to low-temperature flue gas here. The low-temperature flue gas enters the boiler condensing device 3 and performs heat exchange with the water from the normal temperature water tank 5, and then part or all of the flue gas enters the evaporator 11 in the heat pump to exchange heat with the refrigerant working medium to reduce the flue gas temperature, and finally discharged through the flue. The system absorbs waste heat from flue gas, improving its thermal energy quality before using it to heat water tank 6, reducing boiler fuel consumption. The water in normal-temperature water tank 5 exchanges heat with the low-temperature flue gas in boiler condenser 3, raising it to a first target temperature to form preheated water. This water then enters heating water tank 6 for storage. The preheated water then enters condenser 13 of the heat pump unit, exchanging heat with the refrigerant to raise its temperature. After being heated to a second target temperature, it becomes high-temperature water. This high-temperature water flows through deaerator 8 for deoxygenation before being transported to boiler 1 for heating to generate steam. This system also dynamically adjusts flow through on-off valve 7 (connecting heating water tank 6 and condenser 13), air duct valve 9 (connecting boiler condenser 3 and evaporator 11), and fan 10 (located between evaporator 11 and the main exhaust duct) to optimize system energy efficiency.

[0027] Through the intelligent control of the system, the water in the normal temperature water tank 5 is driven by the water pump 4 and circulated in the boiler condensing device 3 to exchange heat with the low-temperature flue gas until it is heated to the first target temperature and then discharged from the normal temperature water tank 5, and then normal temperature water is injected into the normal temperature water tank 5; the preheated water is driven by the water pump 4 and circulated in the condenser 13 to exchange heat with the refrigerant working medium to further increase the water temperature until it is heated to the second target temperature.

[0028] The first target temperature is 40-50°C, and the second target temperature is 70-90°C. They can be set manually according to the season and real-time temperature changes, or they can be intelligently and dynamically controlled by the system.

[0029] The heating water tank 6 comprises a water tank to be heated 6 and a high-temperature water tank. The water tank to be heated 6 is used to temporarily store water reaching a first target temperature flowing out of the normal-temperature water tank 5, while the high-temperature water tank is used to temporarily store water reaching a second target temperature flowing out of the water tank to be heated 6. Furthermore, the water tank to be heated 6 may comprise a plurality of water tanks to be heated, arranged in parallel with the condenser 13 of the heat pump unit. For example, providing two smaller water tanks to be heated 6 and one larger high-temperature water tank can effectively prevent water shortages or insufficient water temperature in the high-temperature water tank.

[0030] The heated water tank 6 is connected to the condenser 13 of the heat pump unit. Driven by the water pump, the preheated water in the heated water tank 6 circulates through the condenser 13 to exchange heat with the refrigerant, raising the preheated water temperature to a second target temperature. The heat pump unit can use refrigerant 744 (carbon dioxide) as a refrigerant.

[0031] After the preheated water in the water tank to be heated 6 is heated to the second target temperature, it flows into the high-temperature water tank for temporary storage, and then the preheated water is injected into the water tank to be heated 6.

[0032] The high-temperature water tank is connected to the economizer 2. The high-temperature water flowing out of the high-temperature water tank is deoxygenated by the deaerator 8, and then is finally heated by the economizer 2 and the high-temperature flue gas before being transported to the boiler.

[0033] The water tanks to be heated 6 are connected to the heat pump unit condenser 13 through an electrically controlled valve. Only one heating water tank 6 is connected to the heat pump unit condenser 13 for heating at the same time.

[0034] The exhaust gas from the deaerator 8 is mixed with the low-temperature flue gas before entering the heat pump unit, thereby recovering and utilizing the waste heat in the exhaust gas from the deaerator 8. The exhaust gas from the deaerator 8 has a temperature similar to that of the low-temperature flue gas, so it can be mixed and utilized before entering the heat pump unit, further improving the waste heat recovery efficiency.

[0035] Summary: Due to the high efficiency of this technical solution, it can be modified on the existing steam boiler system to create considerable economic value. This technical solution can realize the resource utilization of waste flue gas while reducing energy consumption and carbon emissions. Compared with traditional heating methods, flue gas source heat pump technology utilizes the waste heat of waste flue gas, which can save energy and reduce carbon emissions, reduce emissions, improve energy utilization, and has significant economic and environmental benefits. This technical solution uses a flue gas source heat pump through the evaporator. The flue gas source heat pump has its own axial flow fan and uses a smoke pipe to directly extract hot flue gas from the chimney. The flue gas enters the heat pump evaporator and is fully heat-exchanged with the refrigerant inside the heat pump. The exhaust gas temperature can eventually be reduced from 55°C to about 20°C (in winter), fully absorbing a large amount of waste heat and sensible heat in the flue gas. The low-temperature flue gas returns to the main exhaust through the flue gas pipe. Water is introduced into the heat pump through pipes, enters the heat pump condenser to exchange heat with the refrigerant, and can eventually raise the boiler feed water from 40°C to 70°C or even higher. The heated hot water enters the deaerator system through the water supply pipe, meeting the boiler design requirements while improving the thermal efficiency of the waste heat boiler.

[0036] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery, which uses a flue gas source heat pump combined with an evaporator and a condenser to recover the waste heat in the flue gas generated by the boiler to reduce pollution and improve energy utilization, characterized by: include: The heat pump unit, the heat exchange unit and the water storage unit are connected to the flue gas outlet of the boiler, the heat pump unit includes an evaporator and a condenser, the heat exchange unit includes an economizer and a boiler condensing device, and the water storage unit includes at least a normal temperature water tank and a heating water tank; the high-temperature flue gas sent from the boiler enters the economizer and exchanges heat with the water sent from the deaerator, and the high-temperature flue gas is cooled to low-temperature flue gas here, and the low-temperature flue gas enters the boiler condensing device and exchanges heat with the water from the normal temperature water tank, and then part or all of the flue gas enters the evaporator in the heat pump and exchanges heat with the refrigerant to reduce the flue gas temperature, and finally is discharged through the flue; the water in the normal temperature water tank exchanges heat with the low-temperature flue gas in the boiler condensing device, and after rising to a first target temperature, forms preheated water, which enters the heating water tank for storage, and the preheated water enters the condenser of the heat pump unit and exchanges heat with the refrigerant to increase the water temperature, and after being heated to a second target temperature, forms high-temperature water, which flows through the deaerator for deoxygenation treatment and is then transported to the boiler for heating to generate steam; Through intelligent control of the system, the water in the normal temperature water tank is driven by the water pump and circulates in the boiler condensing device to exchange heat with the low-temperature flue gas until it reaches the first target temperature and is discharged from the normal temperature water tank. Then, normal temperature water is injected into the normal temperature water tank; the preheated water is driven by the water pump and circulates in the condenser to exchange heat with the refrigerant to further increase the water temperature until it reaches the second target temperature. The first target temperature is 40-50°C, and the second target temperature is 70-90°C; The heating water tank includes a water tank to be heated and a high-temperature water tank; the water tank to be heated is used to temporarily store water reaching a first target temperature flowing out of the normal-temperature water tank, and the high-temperature water tank is used to temporarily store water reaching a second target temperature flowing out of the water tank to be heated; The water tank to be heated is connected to the condenser of the heat pump unit. The preheated water in the water tank to be heated is circulated in the condenser under the promotion of the water pump to exchange heat with the refrigerant working medium, thereby raising the temperature of the preheated water to the second target temperature. After the preheated water in the water tank to be heated is heated to the second target temperature, it flows into the high-temperature water tank for temporary storage, and then the preheated water is injected into the water tank to be heated.

2. The heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery according to claim 1 is characterized in that: The high-temperature water tank is connected to the economizer. The high-temperature water flowing out of the high-temperature water tank is deoxygenated by the deaerator, and then is finally heated by the economizer and the high-temperature flue gas before being transported to the boiler.

3. The heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery according to claim 1 is characterized in that: The water tanks to be heated include several water tanks arranged in parallel with the condensers of the heat pump units.

4. The heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery according to claim 3 is characterized in that: The water tanks to be heated are connected to the condenser of the heat pump unit through an electrically controlled valve, and only one water tank to be heated is connected to the condenser of the heat pump unit for heating at the same time.

5. The heat pump-deaerator integrated energy-saving system based on steam boiler flue gas waste heat recovery according to claim 1 is characterized in that: The exhaust gas from the deaerator is mixed with the low-temperature flue gas before entering the heat pump unit, thereby recovering and utilizing the waste heat in the exhaust gas from the deaerator.

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