阅读说明：本技术 基于二氧化碳热泵深度余热回收的燃气供暖系统和方法 (Gas heating system and method based on deep waste heat recovery of carbon dioxide heat pump ) 是由 吴彦丽 郝艳红 白静利 陈赞林 赵子萱 康珈 武诗宇 吴少华 于 2020-06-18 设计创作，主要内容包括：本发明公开了一种基于二氧化碳热泵深度余热回收的燃气供暖系统和方法,属于清洁供暖领域。该系统包括：燃气锅炉单元、烟气余热初级回收单元、二氧化碳热泵余热深度回收单元和与之对应的热网回水三级升温管网。该系统采用二氧化碳热泵进一步降低燃气锅炉烟气温度,实现烟气低温排放,同时发挥二氧化碳热泵对低温余热高效提质优势,将低温烟气余热深度高效回收到热网回水中,实现了烟气余热的深度高效回收利用；该系统通过烟气余热分级回收和热网回水分级加热,实现了能量梯级利用,减少了燃气能量的排烟损失,可大幅度提高燃气供暖系统效率,降低燃气供暖成本和燃气供暖污染物排放。(The invention discloses a gas heating system and method based on deep waste heat recovery of a carbon dioxide heat pump, and belongs to the field of clean heating. The system comprises: the system comprises a gas boiler unit, a primary flue gas waste heat recovery unit, a deep carbon dioxide heat pump waste heat recovery unit and a heat supply network backwater three-level heating pipe network corresponding to the deep carbon dioxide heat pump waste heat recovery unit. The system further reduces the flue gas temperature of the gas-fired boiler by adopting the carbon dioxide heat pump, realizes low-temperature emission of the flue gas, simultaneously exerts the high-efficiency upgrading advantage of the carbon dioxide heat pump on low-temperature waste heat, deeply and efficiently recovers the low-temperature flue gas waste heat into the return water of the heat supply network, and realizes deep and efficient recovery and utilization of the flue gas waste heat; the system realizes the gradient utilization of energy through the graded recovery of the waste heat of the flue gas and the graded heating of the return water of the heat supply network, reduces the smoke exhaust loss of the gas energy, can greatly improve the efficiency of a gas heating system, and reduces the gas heating cost and the gas heating pollutant discharge.)

1. The utility model provides a gas heating system based on carbon dioxide heat pump degree of depth waste heat recovery which characterized in that: the system comprises a gas boiler unit, a primary flue gas waste heat recovery unit, a deep carbon dioxide heat pump waste heat recovery unit and a heat supply network backwater three-level heating pipe network corresponding to the deep carbon dioxide heat pump waste heat recovery unit;

the gas boiler unit is used for combusting natural gas and air to generate CO₂、H₂O and high-temperature flue gas containing sulfur and nitrogen compounds simultaneously emit a large amount of heat;

the primary flue gas waste heat recovery unit is used for carrying out heat exchange on high-temperature flue gas and heat supply network return water from a heat user, cooling the high-temperature flue gas to form low-temperature flue gas, and sending the low-temperature flue gas to an evaporation device of the carbon dioxide heat pump waste heat deep recovery unit, and meanwhile, carrying out primary temperature rise on the heat supply network return water from the heat user and sending the low-temperature flue gas to a gas cooling device of the carbon dioxide heat pump waste heat deep recovery unit;

the carbon dioxide heat pump waste heat deep recovery unit comprises a carbon dioxide evaporation device, a throttling device, a carbon dioxide gas cooling device and a compression device, low-temperature flue gas is subjected to heat exchange with a carbon dioxide working medium in the carbon dioxide evaporation device, the temperature of the flue gas is further reduced to be below 30 ℃, heat supply network backwater after the first-stage temperature rise is subjected to heat exchange with high-temperature and high-pressure carbon dioxide fluid in the carbon dioxide gas cooling device, and the heat supply network backwater is sent to the gas boiler unit after the second-stage temperature rise.

2. The gas heating system based on the deep waste heat recovery of the carbon dioxide heat pump as claimed in claim 1, characterized in that:

a natural gas inlet and an excess air inlet are formed in one side of the gas boiler unit, and a high-temperature flue gas outlet formed in the other side of the gas boiler unit is connected with a flue gas waste heat primary recovery unit;

the primary flue gas waste heat recovery unit is a heat exchange device for high-temperature flue gas and heat supply network backwater, and is provided with a high-temperature flue gas inlet, a heat supply network backwater inlet, a low-temperature flue gas outlet and a first-stage heated heat supply network backwater outlet;

the carbon dioxide heat pump waste heat deep recovery unit comprises a carbon dioxide gas cooling device, a throttling device, a carbon dioxide evaporation device and a compression device which are sequentially connected to form a loop; the carbon dioxide gas cooling device is a heat exchange device for the return water of the heat supply network after the first-stage temperature rise and the high-temperature high-pressure carbon dioxide fluid, and a return water outlet of the heat supply network after the first-stage temperature rise is connected with the carbon dioxide gas cooling device; a second-stage heated return water outlet of the gas cooling device is connected with the gas boiler unit; a low-temperature high-pressure carbon dioxide fluid outlet at the outlet of the gas cooling device is connected with a throttling device, the outlet of the throttling device is connected with a carbon dioxide evaporation device, the carbon dioxide evaporation device is a heat exchange device for low-temperature flue gas and low-temperature low-pressure carbon dioxide fluid, a low-temperature flue gas outlet of the flue gas waste heat primary recovery unit is connected with the carbon dioxide evaporation device, a discharged flue gas outlet of the carbon dioxide evaporation device is connected with the atmosphere, and a high-temperature low-pressure carbon dioxide fluid; the outlet of the compression device is connected with a carbon dioxide gas cooling device; the gas boiler unit outputs the backwater of the heat supply network after the third temperature rise, and the outlet of the backwater pipeline of the heat supply network after the third temperature rise is connected with a heat user.

3. The gas heating system based on the deep waste heat recovery of the carbon dioxide heat pump as claimed in claim 2, characterized in that: the low-temperature high-pressure carbon dioxide fluid pipeline of the gas cooling device is connected with the throttling device, the low-temperature low-pressure carbon dioxide fluid pipeline connected with the outlet of the throttling device is connected with the carbon dioxide evaporation device, the high-temperature low-pressure carbon dioxide fluid pipeline connected with the outlet of the carbon dioxide evaporation device is connected with the compression device, and the high-temperature high-pressure carbon dioxide fluid pipeline connected with the outlet of the compression device is connected with the gas cooling device.

4. A fuel gas heating method based on deep waste heat recovery of a carbon dioxide heat pump is adopted in the fuel gas heating system based on deep waste heat recovery of the carbon dioxide heat pump, and the fuel gas heating method is characterized by comprising the following steps:

(1) the natural gas and excess air are fully combusted in the gas boiler unit to produce CO₂、H₂High-temperature flue gas of O and simultaneously emits a large amount of heat；

(2) The high-temperature flue gas material flow in the gas boiler unit is sent to a flue gas waste heat primary recovery unit, the combustion heat is used for carrying out third-stage heating on the heat supply network backwater after the second-stage temperature rise of the carbon dioxide heat pump waste heat deep recovery unit is realized, and the heat supply network backwater is sent to a heat user after the third-stage temperature rise;

(3) the flue gas waste heat primary recovery unit carries out heat exchange on high-temperature flue gas and heat supply network backwater from a heat user, the high-temperature flue gas is cooled to form low-temperature flue gas and is sent to a carbon dioxide evaporation device of the carbon dioxide heat pump waste heat deep recovery unit, and meanwhile, the heat supply network backwater from the heat user is subjected to primary temperature rise and is sent to a gas cooling device of the carbon dioxide heat pump waste heat deep recovery unit;

(4) the low-temperature flue gas exchanges heat with a carbon dioxide working medium in a carbon dioxide evaporation device to become low-temperature flue gas with the temperature of 30 ℃ or below and is led into the atmosphere;

(5) and the backwater of the heat supply network after the first-stage temperature rise is subjected to heat exchange with high-temperature and high-pressure carbon dioxide fluid in a carbon dioxide gas cooling device to form backwater of the heat supply network after the second-stage temperature rise, and the backwater of the heat supply network is sent to the gas boiler unit.

5. The gas heating method based on the deep waste heat recovery of the carbon dioxide heat pump according to claim 4, characterized in that: the gas heating system selects natural gas as raw material, and the low-order heating value of the natural gas is 32.76 MJ/m³When the coefficient of performance COP of the carbon dioxide heat pump is 2.5-6.5, the efficiency of the heating system is 106.6-110%.

Technical Field

The invention relates to a gas heating system and method based on deep waste heat recovery of a carbon dioxide heat pump, and belongs to the field of clean heating.

Background

Along with the acceleration of the urbanization process of China, the scale of urban central heating is continuously enlarged, and meanwhile, the heating in the northern area becomes a main source of pollution emission in winter. The high-efficiency clean heating of northern cities becomes an important content of energy production and consumption revolution. Under the promotion of changing coal into gas, natural gas boilers are adopted in some regional heat source plants, and gas boiler heating gradually becomes a main mode of central heating in the north. However, gas-fired boiler central heating also faces the problems of fuel shortage and high heating cost at present.

At present, the exhaust gas temperature of the gas-fired boiler is between 150 ℃ and 200 ℃, so that a large amount of sensible heat of the exhaust gas is lost due to the high exhaust gas temperature, and the latent heat of water vapor in the exhaust gas is completely wasted. The heat loss of the boiler due to exhaust smoke is the main component of the heat loss of the boiler, and the lost heat can account for 10% -20% of the low-level heating value of natural gas, so that the actual operation heat efficiency of the gas-fired boiler is low and is 80% -90%. The boiler flue gas waste heat recovery has great energy-saving potential. If the exhaust gas temperature is reduced to be below 20-30 ℃, the latent heat of the water vapor in the flue gas is fully recycled, and a good waste heat recovery effect can be achieved.

For the existing gas heat source plant, because the return water temperature of a heat supply network is higher than 60 ℃, the absorption heat pump is utilized to recover the flue gas waste heat for supplying heat to the outside, the recovery amount of the flue gas waste heat is limited, and the utilization amount of the waste heat is seriously influenced.

The carbon dioxide heat pump adopts CO harmless to the environment₂The working medium has high heat transfer efficiency and lower critical temperature (31.1 ℃), as described in Chinese patents CN106568111A and CN 109442530AHas been gradually applied to floor heating and waste heat supply of steam turbines in thermal power plants. The evaporation process of the carbon dioxide heat pump is located in a subcritical area, the heat of low-temperature flue gas of the gas boiler can be absorbed, the deep recovery of low-temperature waste heat of the flue gas is realized, and the fuel utilization rate of a gas heat source plant and the efficiency of a gas heating system are further improved.

Disclosure of Invention

The invention aims to provide a gas heating system based on deep waste heat recovery of a carbon dioxide heat pump, and solves the problems of high exhaust gas temperature, limited utilization of waste heat of exhaust gas, low heating efficiency, high heating cost and the like of a gas heat source plant.

According to the gas heating system based on the deep waste heat recovery of the carbon dioxide heat pump, the temperature of the flue gas of the gas boiler is further reduced by the carbon dioxide heat pump, the low-temperature emission of the flue gas is realized, the advantage of the carbon dioxide heat pump for efficiently improving the low-temperature waste heat is exerted, the low-temperature waste heat of the flue gas is deeply and efficiently recovered into the return water of a heat supply network, and the deep and efficient recovery and utilization of the waste heat of the flue gas are realized; the system realizes the gradient utilization of energy through the graded recovery of the waste heat of the flue gas and the graded heating of the return water of the heat supply network, reduces the smoke exhaust loss of the gas energy, can greatly improve the efficiency of a gas heating system, and reduces the gas heating cost and the gas heating pollutant discharge.

The invention provides a gas heating system based on deep waste heat recovery of a carbon dioxide heat pump, which comprises a gas boiler unit, a primary flue gas waste heat recovery unit, a deep carbon dioxide heat pump waste heat recovery unit and a heat supply network backwater three-level heating pipe network corresponding to the deep carbon dioxide heat pump waste heat recovery unit; wherein the gas boiler unit is used for combusting natural gas and air to generate CO₂、H₂O and high-temperature flue gas containing sulfur and nitrogen compounds, and simultaneously emits a large amount of heat. The high-temperature flue gas stream is sent to a flue gas waste heat primary recovery unit, the combustion heat is used for carrying out third-stage heating on heat supply network backwater after the second-stage heating is realized in a carbon dioxide heat pump waste heat deep recovery unit, and the heat supply network backwater is sent to a heat user after the temperature of the heat supply network backwater is raised by the third stage; the primary flue gas waste heat recovery unit is used for carrying out heat exchange on high-temperature flue gas and return water of a heat supply network from a heat user, and cooling the high-temperature flue gas to form low-temperature flue gas which is sent to the heat supply networkThe evaporation device of the carbon dioxide heat pump waste heat deep recovery unit is used for simultaneously sending the heat supply network backwater which is heated by the first stage and is from the heat user to the gas cooling device of the carbon dioxide heat pump waste heat deep recovery unit; the carbon dioxide heat pump waste heat deep recovery unit comprises a carbon dioxide evaporation device, a throttling device, a carbon dioxide gas cooling device and a compression device, low-temperature flue gas is subjected to heat exchange with a carbon dioxide working medium in the carbon dioxide evaporation device, the temperature of the flue gas is further reduced to be below 30 ℃, heat supply network backwater after the first-stage temperature rise is subjected to heat exchange with high-temperature and high-pressure carbon dioxide fluid in the carbon dioxide gas cooling device, and the heat supply network backwater is sent to the gas boiler unit after the second-stage temperature rise.

In the scheme, a natural gas inlet and an excess air inlet are formed in one side of the gas boiler unit, and a high-temperature flue gas outlet formed in the other side of the gas boiler unit is connected with a flue gas waste heat primary recovery unit;

the primary flue gas waste heat recovery unit is a heat exchange device for high-temperature flue gas and heat supply network backwater, and is provided with a high-temperature flue gas inlet, a heat supply network backwater inlet, a low-temperature flue gas outlet and a first-stage heated heat supply network backwater outlet;

the carbon dioxide heat pump waste heat deep recovery unit comprises a gas cooling device, a throttling device, a carbon dioxide evaporation device and a compression device which are sequentially connected to form a loop; the carbon dioxide gas cooling device is a heat exchange device for the return water of the heat supply network after the first-stage temperature rise and the high-temperature high-pressure carbon dioxide fluid, and a return water outlet of the heat supply network after the first-stage temperature rise is connected with the carbon dioxide gas cooling device; a second-stage heated return water outlet of the gas cooling device is connected with the gas boiler unit; a low-temperature high-pressure carbon dioxide fluid outlet at the outlet of the gas cooling device is connected with a throttling device, the outlet of the throttling device is connected with a carbon dioxide evaporation device, the carbon dioxide evaporation device is a heat exchange device for low-temperature flue gas and low-temperature low-pressure carbon dioxide fluid, a low-temperature flue gas outlet of the flue gas waste heat primary recovery unit is connected with the carbon dioxide evaporation device, a discharged flue gas outlet of the carbon dioxide evaporation device is connected with the atmosphere, and a high-temperature low-pressure carbon dioxide fluid; the outlet of the compression device is connected with a carbon dioxide gas cooling device.

The gas boiler unit outputs the backwater of the heat supply network after the third temperature rise, and the outlet of the backwater pipeline of the heat supply network after the third temperature rise is connected with a heat user.

Furthermore, a low-temperature high-pressure carbon dioxide fluid pipeline of the gas cooling device is connected with the throttling device, a low-temperature low-pressure carbon dioxide fluid pipeline connected with an outlet of the throttling device is connected with the carbon dioxide evaporation device, a high-temperature low-pressure carbon dioxide fluid pipeline connected with an outlet of the carbon dioxide evaporation device is connected with the compression device, and a high-temperature high-pressure carbon dioxide fluid pipeline connected with an outlet of the compression device is connected with the gas cooling device.

The invention provides a gas heating method for deep waste heat recovery of a carbon dioxide heat pump based on the device, which comprises the following steps:

(1) the natural gas and excess air are fully combusted in the gas boiler unit to produce CO₂、H₂High-temperature flue gas of O simultaneously emits a large amount of heat;

(2) the high-temperature flue gas material flow in the gas boiler unit is sent to a flue gas waste heat primary recovery unit, the combustion heat is used for carrying out third-stage heating on the heat supply network backwater after the second-stage temperature rise of the carbon dioxide heat pump waste heat deep recovery unit is realized, and the heat supply network backwater is sent to a heat user after the third-stage temperature rise;

(3) the flue gas waste heat primary recovery unit carries out heat exchange on high-temperature flue gas and heat supply network backwater from a heat user, the high-temperature flue gas is cooled to form low-temperature flue gas and is sent to a carbon dioxide evaporation device of the carbon dioxide heat pump waste heat deep recovery unit, and meanwhile, the heat supply network backwater from the heat user is subjected to primary temperature rise and is sent to a gas cooling device of the carbon dioxide heat pump waste heat deep recovery unit;

(4) the low-temperature flue gas exchanges heat with a carbon dioxide working medium in a carbon dioxide evaporation device to become low-temperature flue gas with the temperature of 30 ℃ or below and is led into the atmosphere;

(5) and the backwater of the heat supply network after the first-stage temperature rise is subjected to heat exchange with high-temperature and high-pressure carbon dioxide fluid in a carbon dioxide gas cooling device to form backwater of the heat supply network after the second-stage temperature rise, and the backwater of the heat supply network is sent to the gas boiler unit.

In the method, the natural gas is selected as the raw material by the gas heating system, and the low-level heating value of the natural gas is 32.76 MJ/m³When the coefficient of performance COP of the carbon dioxide heat pump is 2.5-6.5, the efficiency of the heating system is 106.6-110%.

The invention has the beneficial effects that:

(1) the fuel gas heating system based on the deep waste heat recovery of the carbon dioxide heat pump provided by the invention realizes the energy gradient utilization by adopting the graded recovery of the waste heat of the flue gas and the graded heating of the return water of the heat supply network.

(2) According to the gas heating system based on the deep waste heat recovery of the carbon dioxide heat pump, the temperature of the flue gas is further reduced by arranging the carbon dioxide heat pump, the low-temperature emission of the flue gas is realized, the advantage of the carbon dioxide heat pump for efficiently improving the low-temperature heat is exerted, and the deep and efficient recovery of the low-temperature flue gas waste heat is realized.

(3) According to the gas heating system based on the deep waste heat recovery of the carbon dioxide heat pump, the low-temperature waste heat of the flue gas is recovered into the return water of the heat supply network, so that the deep and efficient recovery and utilization of the flue gas waste heat are realized, the smoke exhaust loss of a gas boiler is reduced, the efficiency of the gas heating system can be greatly improved, and the gas heating cost and the gas heating pollutant emission are reduced.

Drawings

Fig. 1 is a diagram of a gas heating system based on deep waste heat recovery of a carbon dioxide heat pump.

In the figure: the system comprises a gas boiler unit 1, a primary flue gas waste heat recovery unit 2, a gas cooling device 3, a throttling device 4, a carbon dioxide evaporation device 5, a compression device 6 and a user 7, wherein the gas boiler unit is a gas boiler unit;

the natural gas 11, the air 12, the high-temperature flue gas 13, the low-temperature flue gas 14 and the discharged flue gas 15;

16 is heat supply network backwater, 17 is heat supply network backwater after the first-stage temperature rise, 18 is heat supply network backwater after the second-stage temperature rise, and 19 is heat supply network backwater after the third-stage temperature rise;

20 is a low-temperature high-pressure carbon dioxide fluid, 21 is a low-temperature low-pressure carbon dioxide fluid, 22 is a high-temperature low-pressure carbon dioxide fluid, and 23 is a high-temperature high-pressure carbon dioxide fluid.

Detailed Description

The present invention is further illustrated by, but is not limited to, the following examples.