A system for recovering waste heat from flue gas using fresh air enthalpy addition in a gas-fired hot water boiler.

Abstract

This utility model relates to the field of energy-saving technology for heating equipment, specifically a system for recovering waste heat from flue gas using fresh air enthalpy addition in a gas-fired hot water boiler. The system includes a gas-fired hot water boiler body, with a waste heat recovery mechanism installed on the outside of the boiler body. The waste heat recovery mechanism further includes a first-stage condenser, a second-stage condenser, a gas-liquid plate enthalpy adder, a superheated demister, and a circulating pump. The first-stage and second-stage condensers are located on the right side of the top of the gas-fired hot water boiler body, near the flue gas discharge side. The right side of the top of the boiler body is connected to the corresponding first-stage and second-stage condensers. The second-stage condenser is used to recover waste heat from flue gas below 42℃, solving the problem of inefficient recovery of waste heat below 42℃ in existing technologies, improving the thermal efficiency of the boiler system, and reducing natural gas consumption. This system can reduce the exhaust temperature to around 30℃ without a heat pump, recovering approximately 3% of the heat, and has the advantages of simple structure and high energy efficiency.

Description

Technical Field

[0001] This utility model relates to the field of energy-saving technology for heating equipment, specifically a system for recovering waste heat from flue gas by adding enthalpy to fresh air in a gas-fired hot water boiler. Background Technology

[0002] To improve the efficiency of gas-fired hot water boiler systems, companies typically recover waste heat from flue gas by adding economizers to the boiler's tail flue. Most economizers are gas-liquid heat exchangers, which, limited by their heat exchange principle, can only use boiler circulating water to lower the flue gas temperature to near the boiler circulating water return temperature (generally around 40°C), resulting in the waste of remaining heat in the flue gas. Currently, the most common technology for recovering waste heat from flue gas below 42°C is through heat pumps. However, heat pumps have disadvantages such as system complexity, high investment, large space requirements, and inability to operate when outdoor temperatures are high. Utility Model Content

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this utility model provides a system for recovering waste heat from flue gas by adding enthalpy to fresh air in a gas-fired hot water boiler. This system solves the problem of inefficient recovery of waste heat below 42°C in existing technologies, improves the thermal efficiency of the boiler system, reduces natural gas consumption, and thus enhances the practicality of the gas-fired hot water boiler system for recovering waste heat from flue gas by adding enthalpy to fresh air.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, this utility model provides the following technical solution: a system for recovering waste heat from flue gas by adding enthalpy to fresh air in a gas-fired hot water boiler, comprising a gas-fired hot water boiler body, and a waste heat recovery mechanism provided on the outside of the gas-fired hot water boiler body;

[0007] The waste heat recovery mechanism also includes a first-stage condenser, a second-stage condenser, a gas-liquid plate enthalpy generator, a superheated demister, and a circulating pump.

[0008] The gas-fired hot water boiler body has a first-stage condenser and a second-stage condenser installed on the right side of the flue gas discharge side at the top. The right side of the top of the gas-fired hot water boiler body is connected to the corresponding first-stage condenser and second-stage condenser. The second-stage condenser is used to recover waste heat from flue gas below 42°C.

[0009] The gas-fired hot water boiler body is equipped with a gas-liquid plate shell enthalpy heater and a superheated demister on the left side of the fresh air intake side. It is connected to the second-stage condenser through intermediate water circulation to realize fresh air heating and humidification.

[0010] The intermediate water circulation system driven by the circulating pump is used to transfer the waste heat of the flue gas to the fresh air side.

[0011] Furthermore, the improvement of this utility model is that the gas-liquid plate shell enthalpy heater adopts a closed tower structure to saturate and humidify the fresh air and heat it in the first stage, so that the fresh air temperature rises to above 35°C and the relative humidity reaches 100%.

[0012] Furthermore, the present invention includes a burner, wherein the superheated demister performs a second-stage heating of the saturated air to raise its temperature to 42°C and removes the mist, forming superheated air that enters the burner. The burner is connected to the left side of the corresponding gas-fired hot water boiler body, and the burner is connected to the corresponding superheated demister.

[0013] Furthermore, the present invention includes a neutralization tank, wherein the condensate produced by the second-stage condenser is treated by the neutralization tank and then discharged, and the water replenishment for the gas-liquid plate shell enthalpy heater is supplied by municipal tap water.

[0014] (III) Beneficial Effects

[0015] Compared with the prior art, this utility model provides a system for recovering waste heat from flue gas using fresh air enthalpy addition in a gas-fired hot water boiler, which has the following beneficial effects:

[0016] High-efficiency recovery of low-temperature waste heat: It can reduce the flue gas temperature from 42℃ to about 30℃, and the recovered heat accounts for about 3% of the total heat of the system, which significantly improves the boiler thermal efficiency.

[0017] Simplified system structure: It does not rely on heat pumps, and waste heat recovery is achieved through two-stage heat exchange and intermediate water circulation, reducing equipment complexity and investment costs.

[0018] Energy conservation and consumption reduction: Reduce natural gas consumption, lower carbon emissions, and meet environmental protection requirements.

[0019] Highly adaptable: It is not limited by outdoor temperature and can operate stably all year round. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a gas-fired hot water boiler system that utilizes fresh air enthalpy to recover waste heat from flue gas according to this utility model;

[0021] Figure 2 This is a schematic diagram of the first part of a system for recovering waste heat from flue gas using fresh air and enthalpy addition in a gas-fired hot water boiler according to the present invention.

[0022] Figure 3 This is a top view of the structural schematic diagram of a gas-fired hot water boiler system that utilizes fresh air enthalpy to recover waste heat from flue gas according to this utility model.

[0023] In the diagram: 1. Gas-fired hot water boiler body; 2. First-stage condenser; 3. Second-stage condenser; 4. Gas-liquid plate enthalpy heater; 5. Superheated demister; 6. Circulating pump; 7. Burner; 8. Neutralization tank. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] Please see Figure 1-3 A system for recovering waste heat from flue gas by adding enthalpy to fresh air in a gas-fired hot water boiler includes a gas-fired hot water boiler body 1, and a waste heat recovery mechanism is provided on the outside of the gas-fired hot water boiler body 1.

[0026] The waste heat recovery mechanism also includes a first-stage condenser 2, a second-stage condenser 3, a gas-liquid plate enthalpy generator 4, a superheated demister 5, and a circulating pump 6.

[0027] The gas-fired hot water boiler body 1 is provided with a first-stage condenser 2 and a second-stage condenser 3 on the flue gas discharge side on the right side of the top end. The right side of the top end of the gas-fired hot water boiler body 1 is connected to the corresponding first-stage condenser 2 and second-stage condenser 3. The second-stage condenser 3 is used to recover the waste heat of flue gas below 42°C.

[0028] The gas-fired hot water boiler body 1 is equipped with a gas-liquid plate shell enthalpy heater 4 and a superheated demister 5 on the left side of the fresh air inlet side. It is connected to the second-stage condenser 3 through intermediate water circulation to realize fresh air heating and humidification.

[0029] The intermediate water circulation system driven by the circulating pump 6 is used to transfer the waste heat of the flue gas to the fresh air side.

[0030] When this device is in use

[0031] Waste heat recovery pathways:

[0032] When the flue gas temperature drops below 42°C, the second-stage condenser 3 absorbs the waste heat of the flue gas through intermediate water. The intermediate water is then transported by the circulating pump 6 to the gas-liquid plate enthalpy heater 4 and the superheated demister 5, transferring the heat to the intake air of the burner 7.

[0033] Fresh air enthalpy enhancement process:

[0034] Outdoor fresh air at 15°C and RH=50% first enters the gas-liquid plate enthalpy heater 4, where it is heated to 35°C and saturated with humidifier at RH=100%.

[0035] Saturated air enters the superheated demister 5 and is further heated to 42°C in a "superheated state" while removing the mist.

[0036] Heat transfer:

[0037] The heated fresh air enters the burner 7 to participate in combustion, and the heat it carries is transferred to the heating network water through the first-stage condenser 2 to achieve waste heat recovery.

[0038] As a preferred embodiment of the above, the gas-liquid plate shell enthalpy heater 4 adopts a closed tower structure to saturate and humidify the fresh air and heat it in the first stage, so that the fresh air temperature rises to above 35°C and the relative humidity reaches 100%.

[0039] As a preferred embodiment of the above, it also includes a burner 7, wherein the superheated demister 5 performs a second-stage heating of the saturated air to raise its temperature to 42°C and removes the mist, forming superheated air that enters the burner 7. The burner 7 is connected to the left side of the corresponding gas-fired hot water boiler body 1, and the burner 7 is connected to the corresponding superheated demister 5.

[0040] As a preferred embodiment of the above, it also includes a neutralization tank 8, the condensate produced by the second-stage condenser 3 is treated by the neutralization tank 8 and then discharged, and the water replenishment of the gas-liquid plate shell enthalpy heater 4 is supplied by municipal tap water. Detailed Implementation

[0042] Flue gas side modification:

[0043] A second-stage condenser (enthalpy-increasing condenser) is added to the tail flue of the boiler and connected in series with the original first-stage condenser. The flue gas is first cooled to 42°C by the first-stage condenser and then further cooled to about 30°C by the second-stage condenser.

[0044] Fresh air handling process:

[0045] Outdoor fresh air (15℃, H=28.5kJ / kg) enters the gas-liquid plate enthalpy heater through a pipe, and exchanges heat and moisture with intermediate water (28℃), and is heated to 35℃ and humidity 25.79g / kg (H=101.39kJ / kg).

[0046] Saturated air enters the superheated demister, exchanges heat with high-temperature intermediate water (60.22℃), and rises to 42℃ (H=183kJ / kg). At the same time, condensate is removed by the demister device.

[0047] Intermediate water cycle:

[0048] The heat absorbed by the second-stage condenser is transferred to the enthalpy heater and superheated demister through the intermediate water (circulation temperature 28-39℃), forming a closed loop. The power of the circulation pump is matched according to the system heat load.

[0049] Condensate treatment:

[0050] The condensate (with a lower pH value) produced by the second-stage condenser is collected in a neutralization tank, neutralized with alkaline agents, and then meets discharge standards. It is then used as greywater for landscaping or municipal pipe networks.

[0051] First-stage condenser: The return water from the heating network (40℃) enters and absorbs the heat from the high-temperature flue gas, then the temperature rises to 40℃.

[0052] Second-stage condenser: The flue gas temperature drops from 42℃ to 32℃, and the intermediate water absorbs heat and enters the enthalpy cycle;

[0053] Gas-liquid plate enthalpy heater: Fresh air (15℃) is heated and humidified to become 35℃ saturated air (RH=100%);

[0054] Superheated demister: Saturated air is heated to 42°C (RH=100%), and the mist is removed before entering the burner;

[0055] Condensate system: The condensate (30℃, RH=95%) produced by the second-stage condenser is treated by a neutralization tank and then discharged.

[0056] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0057] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0058] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0059] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A system for recovering waste heat from flue gas by adding enthalpy to fresh air in a gas-fired hot water boiler, comprising a gas-fired hot water boiler body (1) and a waste heat recovery mechanism provided on the outside of the gas-fired hot water boiler body (1); Its features are, The waste heat recovery mechanism also includes a first-stage condenser (2), a second-stage condenser (3), a gas-liquid plate enthalpy generator (4), a superheated demister (5), and a circulating pump (6); The gas-fired hot water boiler body (1) is provided with a first-stage condenser (2) and a second-stage condenser (3) on the flue gas discharge side on the right side of the top. The right side of the top of the gas-fired hot water boiler body (1) is connected to the corresponding first-stage condenser (2) and second-stage condenser (3). The second-stage condenser (3) is used to recover the waste heat of flue gas below 42°C. The gas-fired hot water boiler body (1) is equipped with a gas-liquid plate shell enthalpy heater (4) and a superheated demister (5) on the left side of the fresh air inlet side. It is connected to the second-stage condenser (3) through intermediate water circulation to realize fresh air heating and humidification. The intermediate water circulation system driven by the circulating pump (6) is used to transfer the waste heat of flue gas to the fresh air side.

2. The system for recovering waste heat from flue gas using fresh air enthalpy addition in a gas-fired hot water boiler according to claim 1, characterized in that, The gas-liquid plate enthalpy heater (4) adopts a closed tower structure to saturate and humidify the fresh air and heat it in the first stage, so that the fresh air temperature rises to above 35°C and the relative humidity reaches 100%.

3. The system for recovering waste heat from flue gas using fresh air enthalpy addition in a gas-fired hot water boiler according to claim 1, characterized in that, It also includes a burner (7), and the superheated demister (5) heats the saturated air in the second stage, raising its temperature to 42°C and removing the mist, forming superheated air that enters the burner (7). The burner (7) is connected to the left side of the corresponding gas-fired hot water boiler body (1), and the burner (7) is connected to the corresponding superheated demister (5).

4. The system for recovering waste heat from flue gas using fresh air enthalpy addition in a gas-fired hot water boiler according to claim 1, characterized in that, It also includes a neutralization tank (8), the condensate produced by the second-stage condenser (3) is treated by the neutralization tank (8) and then discharged, and the water replenishment of the gas-liquid plate shell enthalpy generator (4) is supplied by municipal tap water.

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