A low-parameter boiler with multiple flue gas recirculation rates

Abstract

This invention discloses a low-parameter boiler with a high flue gas recirculation rate. The boiler's front-stage heating surface, economizer, air preheater, and induced draft fan are sequentially arranged on the flue duct behind the burner and combustion chamber. A flue gas recirculation inlet is located on the flue duct between the combustion chamber and the front-stage heating surface. A flue gas regulating baffle is located on the flue duct before the economizer. A flue gas recirculation outlet is located on the flue duct between the front-stage heating surface and the regulating baffle. The flue gas recirculation inlet and outlet are connected by a bypass pipe equipped with a flue gas recirculation fan. When the boiler is started up, the flue gas regulating baffle closes the flue duct, and the flue gas recirculation fan starts. When the flue gas recirculation rate reaches a set value, the flue gas regulating baffle opens. This invention fully utilizes the waste heat of the tail flue gas, saving heating surface material; reduces exhaust gas temperature, improving boiler efficiency; and significantly reduces NOx generation, achieving energy saving, consumption reduction, high efficiency, and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of waste heat boiler technology, specifically a low-parameter boiler with a high flue gas recirculation rate. Background Technology

[0002] To meet energy conservation and environmental protection requirements, low-parameter boilers are primarily gas-fired boilers. Energy conservation, environmental protection, and reduced steel consumption are key aspects of boiler design for gas-fired boilers. For low-parameter boilers, due to their small capacity, low pressure, and low temperature, large flue gas volume heat exchange is more conducive to saving materials. Therefore, this invention employs a flue gas recirculation coefficient greater than 1, which utilizes the waste heat of the tail flue gas, increases the flue gas flow velocity at the heating surface, enhances heat exchange, and significantly reduces NOx generation. Summary of the Invention

[0003] The problem to be solved by this invention is to provide a low-parameter environmentally friendly gas boiler with a high flue gas recirculation rate. The high flue gas recirculation rate makes full use of the waste heat of the tail flue gas, increases the flue gas velocity on the boiler heating surface, and improves the heat transfer coefficient of the boiler heating surface. At the same time, it greatly reduces NOx generation, has sufficient output, high thermal efficiency, low operating cost, and good environmental performance.

[0004] The technical solution provided by this invention to solve the above problems is as follows: a low-parameter environmentally friendly gas-fired boiler with a high flue gas recirculation rate, comprising a burner and a combustion chamber. A boiler preheating surface, an economizer, an air preheater, and an induced draft fan are sequentially arranged on the flue behind the burner and combustion chamber. A blower is installed at the air inlet of the air preheater, and its outlet is connected to the burner via a pipe. The invention is characterized in that: a flue gas recirculation inlet is provided on the flue between the combustion chamber and the boiler preheating surface; a flue gas regulating baffle for controlling the passage of flue gas is provided on the flue before the economizer; and a flue gas recirculation outlet is provided on the flue between the boiler preheating surface and the flue gas regulating baffle. The flue gas recirculation inlet and outlet are connected by a bypass pipe, and a flue gas recirculation fan is installed on the bypass pipe. The flue gas regulating baffle and the flue gas recirculation fan are controlled by an electric control device. When the boiler is started up, the flue gas regulating baffle closes the flue, and the flue gas recirculation fan starts. When the flue gas recirculation rate reaches a set value, the flue gas regulating baffle opens, and the boiler operates normally.

[0005] Furthermore, the flue gas recirculation ratio value set by the electric control device of the flue gas regulating baffle is greater than 1.

[0006] Furthermore, a portion of the recirculated flue gas introduced from the flue gas recirculation outlet by the flue gas recirculation fan is led out through a bypass pipe to a branch of the burner and then into the burner, thereby reducing NOx generation.

[0007] Furthermore, the burner and combustion chamber are equipped with either an adiabatic furnace or an endothermic furnace according to the high or low calorific value of the gas.

[0008] Furthermore, the boiler front-stage heating surface may or may not have a superheater (for saturated steam boilers) depending on the boiler parameters, or an economizer may be added.

[0009] The principle of this invention is as follows: Flue gas recirculation involves drawing gas from the recirculation outlet and mixing it with combustion-generated flue gas at the recirculation inlet. A small amount is returned to the burner to reduce NOx production, significantly increasing the inlet enthalpy of the boiler's front-stage heating surface. This increases the enthalpy per unit medium on the boiler's front-stage heating surface, meaning that the large volume of flue gas improves heat transfer and saves on heating surface materials. Furthermore, the suitable inlet flue gas temperature and low heating surface wall temperature reduce the need for large amounts of alloy materials in the tubing. Simultaneously, the exhaust gas temperature is easily reduced, increasing boiler efficiency.

[0010] The beneficial effects of this invention are: compared with the prior art, this invention makes full use of the waste heat of the tail flue gas, saves heating surface materials; reduces the exhaust gas temperature and improves boiler efficiency; at the same time, it greatly reduces NOx generation; and achieves energy saving, consumption reduction, high efficiency and environmental protection performance. Attached Figure Description

[0011] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0012] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0013] The attached diagram is labeled as follows: 1. Combustion chamber, 2. Flue gas recirculation inlet, 3. Boiler front heating surface, 4. Flue gas recirculation outlet, 5. Flue gas regulating damper, 6. Economizer, 7. Air preheater, 8. Induced draft fan, 9. Blower, 10. Flue gas recirculation fan, 11. Burner. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] like Figure 1As shown, a low-parameter boiler with a high flue gas recirculation rate includes a burner 11 and a combustion chamber 1. A boiler front-stage heating surface 3, an economizer 6, an air preheater 7, and an induced draft fan 8 are sequentially arranged on the flue duct behind the burner 11 and combustion chamber 1. A blower 9 is installed at the air inlet of the air preheater 7, and its outlet is connected to the burner 11 via a pipe. A flue gas recirculation inlet 2 is provided on the flue duct between the combustion chamber 1 and the boiler front-stage heating surface 3. A flue gas regulating baffle 5 for controlling the flow of flue gas is installed on the flue duct before the economizer 6. A flue gas recirculation outlet 4 is provided on the flue between the boiler front heating surface 3 and the flue gas regulating baffle 5; the flue gas recirculation inlet 2 and the flue gas recirculation outlet 4 are connected by a bypass pipe and a flue gas recirculation fan 10 is provided on the bypass pipe; the flue gas regulating baffle 5 and the flue gas recirculation fan 10 are controlled by an electric control device. When the boiler is started, the flue gas regulating baffle 5 closes the flue and the flue gas recirculation fan 10 turns on. When the flue gas recirculation ratio reaches the set value, the flue gas regulating baffle 5 turns on and the boiler operates normally.

[0016] The electric control device for the flue gas regulating baffle 5 is set with a flue gas recirculation ratio greater than 1.

[0017] The flue gas recirculation fan 10 introduces a portion of the recirculated flue gas from the flue gas recirculation outlet 4, which is then led out through a bypass pipe to a branch of the burner and into the burner 11, thereby reducing NOx generation.

[0018] The burner 11 and combustion chamber 1 are equipped with either an insulated furnace or an absorbent furnace according to the high or low calorific value of the gas.

[0019] The boiler front heating surface 3 may or may not have a superheater (for saturated steam boilers) depending on the boiler parameters, or an economizer may be added.

[0020] This invention utilizes flue gas recirculation by extracting the gas from the recirculation outlet 4 and mixing it with the combustion-generated flue gas at the recirculation inlet 2. A small amount is returned to the burner to reduce NOx production. This significantly increases the enthalpy of the flue gas at the boiler's front-stage heating surface 3, resulting in a higher enthalpy per unit medium on the boiler's front-stage heating surface. This means that the increased flue gas volume improves heat transfer and saves on heating surface materials. Furthermore, the suitable inlet flue gas temperature and low heating surface wall temperature reduce the need for large amounts of alloy materials in the tubing. Simultaneously, the exhaust gas temperature is easily reduced, increasing boiler efficiency. This invention effectively utilizes the waste heat of the tail flue gas, saving on heating surface materials, while significantly reducing NOx production, achieving energy saving, high efficiency, and environmental protection.

[0021] 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 variations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents. The terms "inlet," "outlet," "front," "tail," or other terms expressing positional relationships used in the invention are only for better describing the relative positional relationships of the various structures or processes in the invention, and do not mean that any component of the invention is located in an absolute position before or after.

Claims

1. A low-parameter environmentally friendly gas-fired boiler with a high flue gas recirculation rate, comprising a burner and a combustion chamber, wherein a boiler front-stage heating surface, an economizer, an air preheater, and an induced draft fan are sequentially arranged on the flue behind the burner and combustion chamber; the air preheater has a blower at its inlet and its outlet connected to the burner via a pipe; characterized in that: A flue gas recirculation inlet is provided on the flue between the combustion chamber and the boiler's front heating surface. A flue gas regulating damper for controlling the passage of flue gas is provided on the flue before the economizer. A flue gas recirculation outlet is provided on the flue between the boiler's front heating surface and the flue gas regulating damper. The flue gas recirculation inlet and outlet are connected by a bypass pipe, and a flue gas recirculation fan is provided on the bypass pipe. The flue gas regulating damper and the flue gas recirculation fan are controlled by an electric control device. When the boiler is started up, the flue gas regulating damper closes the flue and the flue gas recirculation fan starts. When the flue gas recirculation ratio reaches the set value, the flue gas regulating damper opens and the boiler operates normally.

2. The low-parameter environmentally friendly gas-fired boiler with multiple flue gas recirculation rates according to claim 1, characterized in that: The electric control device for the flue gas regulating baffle is set with a flue gas recirculation ratio greater than 1.

3. The low-parameter environmentally friendly gas-fired boiler with multiple flue gas recirculation rates according to claim 1, characterized in that: A portion of the recirculated flue gas introduced from the flue gas recirculation outlet by the flue gas recirculation fan is led out through a bypass pipe to a branch of the burner and then into the burner.

4. The low-parameter environmentally friendly gas-fired boiler with multiple flue gas recirculation rates according to claim 1, characterized in that: The burner and combustion chamber are equipped with either an insulated furnace or an absorbent furnace based on the high or low calorific value of the gas.

5. A low-parameter environmentally friendly gas-fired boiler with multiple flue gas recirculation rates according to claim 1, characterized in that: The boiler front-stage heating surface may or may not have a superheater, depending on the boiler parameters, or an economizer may be added.

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