Flue gas condensation waste heat recovery system

Abstract

A flue gas condensation waste heat recovery system comprises a boiler and a flue gas condensation device. A gas phase outlet of the boiler is connected with a gas phase inlet of the flue gas condensing device through a pipeline, a liquid phase outlet of the boiler is connected to the outside of the system, and a liquid phase inlet of the flue gas condensing device is connected with a heating water return pipe; the flue gas condensing device comprises an energy saver, a condensing heat exchanger and a direct-fired heat pump; a gas phase outlet of the boiler is connected with a gas phase inlet of the energy saver through a pipeline, a gas phase outlet of the energy saver is connected with a gas phase inlet of the condensation heat exchanger through a pipeline, and the direct-fired heat pump is connected with the condensation heat exchanger through a loop. Through the arrangement, the problem that the energy-saving effect is poor due to the fact that vaporization latent heat of a large amount of water vapor in smoke is not recycled and the waste heat recycling effect is poor can be effectively solved.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas recovery, and in particular to a flue gas condensation waste heat recovery system. Background Art

[0002] In urban heating projects, the exhaust gas temperature of the boiler under rated conditions is generally not lower than 150°C. Excessively high exhaust gas temperature increases the heat loss of the exhaust gas, resulting in reduced boiler thermal efficiency. The emission of a large amount of high-temperature flue gas not only causes a large amount of heat energy waste, but also pollutes the environment.

[0003] In order to solve this problem, the flue gas waste heat recovery device installed in the boiler room coal-to-gas project uses primary return water as a low-temperature heat source to exchange heat with the flue gas. Since the primary return water temperature is relatively high, the flue gas temperature is still relatively high after recovery. At the same time, since a large amount of latent heat of vaporization of water vapor in the flue gas is not recovered, the waste heat recovery effect is poor, resulting in poor energy-saving effects. Utility Model Content

[0004] In view of this, the present application proposes a flue gas condensation waste heat recovery system, which can better recover the waste heat of the flue gas.

[0005] According to one aspect of the present application, a flue gas condensation waste heat recovery system is provided, comprising a boiler and a flue gas condensing device; a pipeline is connected between the gas phase outlet of the boiler and the gas phase inlet of the flue gas condensing device, a liquid phase outlet of the boiler is connected to the outside of the system, and a liquid phase inlet of the flue gas condensing device is connected to a heating return pipe; the flue gas condensing device comprises an economizer, a condensing heat exchanger and a direct-fired heat pump; a pipeline is connected between the gas phase outlet of the boiler and the gas phase inlet of the economizer, a pipeline is connected between the gas phase outlet of the economizer and the gas phase inlet of the condensing heat exchanger, and a loop is connected between the direct-fired heat pump and the condensing heat exchanger; the inlet end of the direct-fired heat pump is connected to natural gas that provides low-temperature water, and the number of liquid phase outlets of the condensing heat exchanger is two, and the flue gas after waste heat recovery is discharged through the outlet end of the condensing heat exchanger, and the moisture in the flue gas is condensed and discharged through the second liquid phase outlet of the condensing heat exchanger.

[0006] In a possible implementation, the number of the liquid phase inlet and the liquid phase outlet of the direct-fired heat pump are both two, the first liquid phase inlet of the direct-fired heat pump is connected to the heating return pipe, the first liquid phase outlet of the direct-fired heat pump is connected to the liquid phase inlet of the condensing heat exchanger by a pipeline, the second liquid phase inlet of the direct-fired heat pump is connected to the first liquid phase outlet of the condensing heat exchanger by a pipeline, and the second liquid phase outlet of the direct-fired heat pump is connected to the liquid phase inlet of the boiler by a pipeline.

[0007] In a possible implementation, a circulation pump is provided between the direct-fired heat pump and the condensing heat exchanger.

[0008] In a possible implementation, the first liquid phase outlet of the condensing heat exchanger is connected to the liquid phase inlet of the circulation pump by a pipeline, and the liquid phase outlet of the circulation pump is connected to the second liquid phase inlet of the direct-fired heat pump by a pipeline.

[0009] In a possible implementation, the circulating pump is also arranged between the direct-fired heat pump and the heating return pipe, and the number of liquid phase outlets of the circulating pump between the direct-fired heat pump and the heating return pipe is two; the first liquid phase outlet of the circulating pump between the direct-fired heat pump and the heating return pipe is connected by a pipeline to the first liquid phase inlet of the direct-fired heat pump, and the second liquid phase outlet of the circulating pump between the direct-fired heat pump and the heating return pipe is connected by a pipeline to the liquid phase inlet of the boiler.

[0010] In a possible implementation, one boiler, one economizer, and one condensing heat exchanger form a flue gas flow group, and a plurality of flue gas flow groups are provided.

[0011] In a possible implementation, the number of the condensing heat exchangers is one more than the number of the flue gas flow groups.

[0012] In a possible implementation, the condensing heat exchanger includes a heat exchanger and a heat exchange medium channel, and the heat exchanger and the heat exchange medium channel are connected by a pipeline.

[0013] In a possible implementation, a plurality of fins are disposed in the heat exchanger.

[0014] In a possible implementation, the direct-fired heat pump includes a direct-fired generator, a condenser, an evaporator, and an absorber, and the direct-fired generator, condenser, evaporator, and absorber are connected in sequence by pipelines.

[0015] The beneficial effects of the utility model are as follows: by adding a flue gas condensing heat exchanger and a direct-fired heat pump, the boiler heats the water in the boiler, the heated water is connected to the outside through the liquid phase outlet of the boiler, the generated high-temperature flue gas is sent to the economizer through the gas phase outlet of the boiler, the economizer recovers the sensible heat of the high-temperature flue gas, the flue gas after the first cooling is sent to the flue gas condensing heat exchanger through the gas phase outlet of the economizer, and at the same time, low-temperature water is transmitted to the flue gas condensing heat exchanger through the direct-fired heat pump, the low-temperature water cools the flue gas for the second time, the flue gas after the second cooling is discharged through the outlet end of the flue gas condensing heat exchanger, the water in the flue gas is condensed and discharged through the second liquid phase outlet of the condensing heat exchanger; the low-temperature water at this time is heated and returned to the direct-fired heat pump again; at the same time, the return water of the heat network is divided into two branches, one of which enters the direct-fired heat pump for heating, and then is mixed with the other branch after heating and enters the boiler; the low-temperature water produced by the direct-fired heat pump participates in the secondary heat exchange of the flue gas condensing heat exchanger, which solves the problem that a large amount of latent heat of vaporization of water vapor in the flue gas is not recovered, the waste heat recovery effect is poor, and the energy-saving effect is not good.

[0016] Other features and aspects of the present application will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The utility model is a thermal flow diagram. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0019] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of the present invention, it is necessary to understand that the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention or 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 invention.

[0021] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0022] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix", "join", "hinge" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] like Figure 1 As shown, the flue gas condensation waste heat recovery system includes a boiler 100 and a flue gas condensation device 200; the gas phase outlet of the boiler 100 is connected to the gas phase inlet of the flue gas condensation device 200 by a pipeline, the liquid phase outlet of the boiler 100 is connected to the outside of the system, and the liquid phase inlet of the flue gas condensation device 200 is connected to the heating return pipe 300; the flue gas condensation device 200 includes an economizer 210, a condensing heat exchanger 220 and a direct-fired heat pump 230; the gas phase outlet of the boiler 100 is connected to the gas phase inlet of the economizer 210 The outlets are connected by pipelines, the gas phase outlet of the economizer 210 is connected to the gas phase inlet of the condensing heat exchanger 220 by pipelines, and the direct-fired heat pump 230 is loop-connected to the condensing heat exchanger 220; the inlet end of the direct-fired heat pump 230 is connected to the natural gas that provides low-temperature water, and the condensing heat exchanger 220 has two liquid phase outlets, and the flue gas after waste heat recovery is discharged through the outlet end of the condensing heat exchanger 220, and the moisture in the flue gas is condensed and discharged through the second liquid phase outlet of the condensing heat exchanger 220.

[0024] Specifically, the gas phase outlet of the boiler 100 is connected to the gas phase inlet of the flue gas condensing device 200 by a pipeline, and the liquid phase outlet of the boiler 100 is connected to the heating water supply pipe 300. When the boiler 100 heats the water to the required temperature, the flue gas enters the flue gas condensing device 200 through the pipeline from the gas phase outlet of the boiler 100, and the heated water is discharged from the boiler 100 to the outside of the system and enters the heating system to start heating; the heating return water pipe 300 is connected to the liquid phase inlet of the flue gas condensing device 200, and the heat network return water of the heating return water pipe 300 enters the flue gas condensing device 200;

[0025] The flue gas condensing device 200 includes an economizer 210, a condensing heat exchanger 220 and a direct-fired heat pump 230; the gas phase outlet of the boiler 100 is connected to the gas phase inlet of the economizer 210 by a pipeline, and the high-temperature flue gas generated after the boiler 100 heats the water enters the economizer 210 through a pipeline, and the economizer 210 recovers the sensible heat of the high-temperature flue gas and reduces the temperature of the high-temperature flue gas from about 120°C to about 55°C; the gas phase outlet of the economizer 210 is connected to the gas phase inlet of the condensing heat exchanger 220 by a pipeline, and the flue gas at 55°C enters the condensing heat exchanger 220 through a pipeline, and the direct-fired heat pump 230 is connected to the condensing heat exchanger 2 20 are connected in a loop, and the 12°C low-temperature circulating water provided by the direct-fired heat pump 230 is used to exchange heat with the 55°C flue gas, so as to absorb the low-temperature sensible heat and latent heat in the 55°C flue gas, so as to reduce the flue gas temperature from 55°C to about 30°C; the inlet end of the direct-fired heat pump 230 is connected to the natural gas of the geotechnical low-temperature water, and the inlet end of the direct-fired heat pump 230 burns natural gas to produce 12°C low-temperature water. The number of liquid phase outlets of the condensing heat exchanger 220 is two, and the flue gas after waste heat recovery is discharged through the outlet end of the condensing heat exchanger 220, and the moisture in the flue gas is condensed and discharged out of the system through the second liquid phase outlet of the condensing heat exchanger 220, and is used for water replenishment of the primary system and the secondary system after treatment.

[0026] In a possible implementation, the number of the liquid phase inlet and the liquid phase outlet of the direct-fired heat pump 230 are both two, the first liquid phase inlet of the direct-fired heat pump 230 is connected to the heating return pipe 300, the first liquid phase outlet of the direct-fired heat pump 230 is connected to the liquid phase inlet of the condensing heat exchanger 220 by a pipeline, the second liquid phase inlet of the direct-fired heat pump 230 is connected to the first liquid phase outlet of the condensing heat exchanger 220 by a pipeline, and the second liquid phase outlet of the direct-fired heat pump 230 is connected to the liquid phase inlet of the boiler 100 by a pipeline.

[0027] Specifically, Figure 1 As shown, because the liquid phase outlet of the direct-fired heat pump 230 is to be connected to the liquid phase inlet of the condensing heat exchanger 220 and the liquid phase inlet of the boiler 100 through a pipeline, the liquid phase outlet of the direct-fired heat pump 230 is to be set to two; because the liquid phase inlet of the direct-fired heat pump 230 is connected to the first liquid phase outlet of the condensing heat exchanger 230 and the heating return pipe 300, the liquid phase inlet of the direct-fired heat pump 230 is also to be set to two.

[0028] In a possible implementation, a circulating pump 240 is arranged between the direct-fired heat pump 230 and the condensing heat exchanger 200; the first liquid phase outlet of the condensing heat exchanger 220 is connected to the liquid phase inlet of the circulating pump 240 by a pipeline, and the liquid phase outlet of the circulating pump 240 is connected to the second liquid phase inlet of the direct-fired heat pump 230 by a pipeline.

[0029] Specifically, Figure 1 As shown, the direct-fired heat pump 230 is driven by natural gas to produce 12°C low-temperature water and send it to the condensing heat exchanger 220. The 12°C low-temperature water cools the flue gas from 55°C to 30°C, recovers heat, and then raises the temperature to 20°C, and then is sent to the direct-fired heat pump 230 through the circulation pump 240.

[0030] In a possible implementation, the circulation pump 240 is also arranged between the direct-fired heat pump 230 and the heating return pipe 300, and the number of liquid phase outlets of the circulation pump 240 between the direct-fired heat pump 230 and the heating return pipe 300 is two; the first liquid phase outlet of the circulation pump 240 between the direct-fired heat pump 230 and the heating return pipe 300 is connected by a pipeline to the first liquid phase inlet of the direct-fired heat pump 230, and the second liquid phase outlet of the circulation pump 240 between the direct-fired heat pump 230 and the heating return pipe 300 is connected by a pipeline to the liquid phase inlet of the boiler 100.

[0031] Specifically, Figure 1 As shown, because the circulation pump 240 between the direct-fired heat pump 230 and the heating return water pipe 400 divides the heat network return water of the heating return water pipe 300 into two branches, one branch enters the direct-fired heat pump 230, is heated to 60°C by the direct-fired heat pump 230, is mixed with the other branch, and then enters the boiler 100 for heating.

[0032] In a possible implementation, one boiler 100, one economizer 210, and one condensing heat exchanger 220 form a flue gas flow group, and a plurality of flue gas flow groups are provided.

[0033] Specifically, Figure 1 As shown, in the vertical direction, one boiler 100, one economizer 210, and one condensing heat exchanger 220 form a flue gas flow group. According to actual needs, multiple flue gas flow groups can be set to improve work efficiency.

[0034] In a possible implementation, the number of the condensing heat exchangers 220 is one more than the number of the flue gas flow groups.

[0035] Specifically, Figure 1As shown, because the direct-fired heat pump 230 also generates high-temperature flue gas during operation and the waste heat needs to be recovered, an additional condensing heat exchanger 220 is provided to absorb the waste heat of the flue gas of the direct-fired heat pump 230 .

[0036] In one possible implementation, the condensing heat exchanger 220 includes a heat exchanger and a heat exchange medium channel, and the heat exchanger and the heat exchange medium channel are connected by a pipeline; fins are arranged inside the heat exchanger; wherein, the heat exchanger is the core component of the economizer 210, and is usually made of high-efficiency heat transfer materials. The fins are arranged inside the heat exchanger because the finned tubes increase the heat exchange area and improve the heat exchange efficiency.

[0037] In a possible implementation, the direct-fired heat pump 230 includes a direct-fired generator, a condenser, an evaporator, and an absorber, and the direct-fired generator, condenser, evaporator, and absorber are connected in sequence by pipelines. The principle of the absorption heat pump is as follows: the refrigerant water enters the high vacuum environment of the evaporator, absorbs the heat of the low-temperature water and evaporates into refrigerant steam. The refrigerant steam enters the absorber and is absorbed by the concentrated lithium bromide solution from the generator, releasing heat to heat the heating return water. The solution pump pumps the diluted solution to the generator and is heated by the gas heat source to produce refrigerant steam and concentrated solution. The refrigerant steam enters the condenser to condense into refrigerant water and releases heat to heat the heating return water again, and the refrigerant water enters the evaporator to evaporate again and absorb the heat of the low-temperature water. Since the heat of the hot water comes from two parts: one part recovers the heat of the low-temperature heat source, and the other part comes from the driving heat source. Therefore, the COP (hot water heat / driving heat) of the absorption heat pump heating can reach 1.6 to 1.8, which shows that the absorption heat pump heating has a huge energy-saving advantage.

[0038] When using the utility model: select a direct-fired lithium bromide absorption heat pump unit with a rated waste heat recovery capacity of 4 million kcal / h to recover the waste heat of flue gas. The original flue gas waste heat recovery device at the exhaust port of a 29MW gas-fired hot water boiler is used as a first-level energy saver, and a second-level flue gas condensing heat exchanger is set afterwards. The direct-fired heat pump is driven by natural gas to produce 12°C low-temperature water and send it to the second-level flue gas condensing heat exchanger. The 12°C low-temperature water cools the flue gas from 55°C to 30°C and recovers heat, then heats it to 20°C, and then sends it to the direct-fired heat pump through a circulation pump to form a waste heat recovery cycle. The 45°C heat network return water is divided into two branches, one enters the heat pump unit, and after being heated to 60°C by the heat pump, it is mixed with the other branch and then enters the boiler for heating; after the boiler exhaust is recovered through two-stage condensation waste heat, the flue gas temperature is reduced, and the water in the flue gas is condensed and recovered to the condensing water tank, and after treatment, it is used for water replenishment in the primary system and the secondary system.

[0039] The above arrangement forms the utility model. After the exhaust gas of the boiler is recovered through two-stage condensation waste heat, the flue gas temperature drops to below 30°C, and the thermal efficiency of the boiler is increased by about 13%. After cooling by the heat pump, 80% of the water vapor in the flue gas is removed, and the moisture in the flue gas is condensed and recovered to the condensation water tank, which is used for water replenishment of the primary system and the secondary system after treatment. Therefore, this system is of great significance for energy saving, water saving, and improving the comprehensive utilization efficiency of the system. In addition, the flue gas condensation also plays a role in eliminating white smoke and reducing pollutant emissions. This transformation method can alleviate energy pressure and improve air quality for the form of gas boiler heating in the north. It has important practical significance.

[0040] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and concept of the present invention within the scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A flue gas condensation waste heat recovery system, characterized in that: Includes boiler and flue gas condensing plant; The gas phase outlet of the boiler is connected to the gas phase inlet of the flue gas condensing device by a pipeline, the liquid phase outlet of the boiler is connected to the outside of the system, and the liquid phase inlet of the flue gas condensing device is connected to a heating return pipe; The flue gas condensing device includes an economizer, a condensing heat exchanger and a direct-fired heat pump; The gas phase outlet of the boiler is connected to the gas phase inlet of the economizer by a pipeline, the gas phase outlet of the economizer is connected to the gas phase inlet of the condensing heat exchanger by a pipeline, and the direct-fired heat pump is connected to the condensing heat exchanger by a loop; The inlet end of the direct-fired heat pump is connected to natural gas that provides low-temperature water. The number of liquid phase outlets of the condensing heat exchanger is two. The flue gas after waste heat recovery is discharged through the outlet end of the condensing heat exchanger, and the moisture in the flue gas is condensed and discharged through the second liquid phase outlet of the condensing heat exchanger.

2. The flue gas condensation waste heat recovery system according to claim 1, characterized in that: The number of the liquid phase inlet and the liquid phase outlet of the direct-fired heat pump are both two. The first liquid phase inlet of the direct-fired heat pump is connected to the heating return pipe, the first liquid phase outlet of the direct-fired heat pump is connected to the liquid phase inlet of the condensing heat exchanger by a pipeline, the second liquid phase inlet of the direct-fired heat pump is connected to the first liquid phase outlet of the condensing heat exchanger by a pipeline, and the second liquid phase outlet of the direct-fired heat pump is connected to the liquid phase inlet of the boiler by a pipeline.

3. The flue gas condensation waste heat recovery system according to claim 2, characterized in that: A circulation pump is arranged between the direct-fired heat pump and the condensing heat exchanger.

4. The flue gas condensation waste heat recovery system according to claim 3, characterized in that: The first liquid phase outlet of the condensing heat exchanger is connected to the liquid phase inlet of the circulating pump by a pipeline, and the liquid phase outlet of the circulating pump is connected to the second liquid phase inlet of the direct-fired heat pump by a pipeline.

5. The flue gas condensation waste heat recovery system according to claim 4, characterized in that: The circulation pump is also arranged between the direct-fired heat pump and the heating water return pipe, and the number of liquid phase outlets of the circulation pump between the direct-fired heat pump and the heating water return pipe is two; The first liquid phase outlet of the circulating pump between the direct-fired heat pump and the heating return pipe is connected to the first liquid phase inlet of the direct-fired heat pump by a pipeline, and the second liquid phase outlet of the circulating pump between the direct-fired heat pump and the heating return pipe is connected to the liquid phase inlet of the boiler by a pipeline.

6. The flue gas condensation waste heat recovery system according to any one of claims 1 to 5, characterized in that: One boiler, one economizer, and one condensing heat exchanger form a flue gas flow group, and a plurality of flue gas flow groups are provided.

7. The flue gas condensation waste heat recovery system according to claim 6, characterized in that: The number of the condensing heat exchangers is one more than the number of the flue gas flow groups.

8. The flue gas condensation waste heat recovery system according to any one of claims 1 to 5, characterized in that: The condensing heat exchanger comprises a heat exchanger and a heat exchange medium channel, and the heat exchanger and the heat exchange medium channel are connected by a pipeline.

9. The flue gas condensation waste heat recovery system according to claim 8, characterized in that: A plurality of fins are arranged in the heat exchanger.

10. The flue gas condensation waste heat recovery system according to any one of claims 1 to 5, characterized in that: The direct-fired heat pump comprises a direct-fired generator, a condenser, an evaporator, and an absorber, and the direct-fired generator, condenser, evaporator, and absorber are connected in sequence by pipelines.

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