External steam preheater system for improving hot air temperature of boiler by superheated steam

Abstract

The application discloses an external steam preheater for improving hot air temperature of a boiler by using superheated steam, which comprises a superheater and an air preheater located in a flue, and is characterized in that an input pipe of the superheater is connected to a boiler drum, a drain trap is arranged at an output pipe part of the superheater, the drain trap is divided into two output paths, one path enters a drain collecting box, and the other path is connected to the steam preheater; meanwhile, the output pipe of the air preheater is conveyed to the boiler air inlet after passing through the steam preheater, so that the primary air temperature is further heated; and the steam pipe output from the steam preheater is connected to a gas supply main pipe. The superheated steam is connected to an independent steam preheater through a drain pipe, the excess steam heat is converted to the primary air, the primary air temperature is improved, the combustion condition of the boiler is improved, and the burnout degree is greatly improved. Under the premise that the self energy consumption is not needed, the steam supply requirement is met, the boiler efficiency is improved, the structure is simple, the air duct parameters are not affected, the whole system is connected to the network and is easy to control, and the energy saving is obvious.

Description

Technical Field

[0001] The invention relates to a thermal power generation energy-saving technology, in particular to an external steam preheater system which utilizes superheated steam to increase the temperature of boiler hot air. Background Art

[0002] In thermal power plants using boilers, steam output from the boiler drum is typically 3.2 MPa. After passing through the superheater, it reaches a temperature of approximately 420°C and is supplied to the steam turbine. To ensure normal turbine air supply, the steam exported to the main supply pipe is typically extracted from turbines 1 and 2. However, the steam delivered from the main supply pipe only requires 0.8 MPa and 300°C to fully meet operating requirements. However, the steam temperature of the superheater is generally around 400°C. A small amount of steam is heated in the superheater drain pipe to raise the boiler inlet air temperature before being fed into the heating pipe. This aspect of energy utilization is virtually nonexistent in existing boiler power generation systems. Furthermore, in actual boiler power generation systems, internal preheaters are often installed to increase the primary or secondary air temperature. These preheaters are not only installed in high-pressure areas but also consume their own energy.

[0003] It is worth noting that there is an inevitable connection between the boiler inlet air temperature and energy consumption. Under the condition of ensuring the oxygen content, high inlet air temperature can improve the combustion conditions. Heating the primary air is an example. Increasing the inlet air temperature can increase the combustion degree, thereby improving the overall working efficiency of the boiler.

[0004] Furthermore, existing pre-heaters are typically used in grate-type waste incinerators. These typically draw steam from the upper drum or primary exhaust of the turbine, using supercooled condensate to enter a drain tank, where it is pumped to the deaerator. Designing based on this approach would require significant modification work, a long time, and high costs. Furthermore, installation on a pressure vessel clearly imposes higher construction requirements. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems and provide an external steam preheater system that uses superheated steam to increase the temperature of the boiler hot air. It uses the temperature difference after drainage and then supplies heat to the heat network to re-heat the boiler primary air. The external structure is simple and easy to maintain and control.

[0006] The above technical problems of the present invention are mainly solved by the following technical solutions: an external preheater system that uses superheated steam to increase the temperature of boiler hot air, including a superheater and an air preheater located in the flue, which is characterized in that the superheater input pipe is connected to the boiler steam drum, and a steam trap is provided at the superheater output pipe. The steam is output from the superheater drain pipe in two ways, one way enters the drain header, and the other way is connected to the preheater; at the same time, the air preheater output pipe passes through the preheater and then is transported to the boiler air inlet, so that the primary air temperature is further heated; the steam pipe output from the preheater is connected to the gas supply main pipe.

[0007] In the aforementioned external pre-steamer system that utilizes superheated steam to increase the temperature of the boiler hot air, preferably, the pre-steamer is a heat exchange device independent of other heat exchange systems.

[0008] In the aforementioned external steam preheater system that utilizes superheated steam to increase the temperature of the hot air from the boiler, preferably, the air preheater is connected to the primary fan.

[0009] In the aforementioned external preheater system that utilizes superheated steam to increase the temperature of the boiler hot air, preferably, pressure gauges and thermometers are provided at the steam input and output pipes, and the air input and output pipes of the preheater.

[0010] In the aforementioned external preheater system that utilizes superheated steam to increase the temperature of the boiler hot air, preferably, the preheater includes a straight-tube steam and air heat exchange device integrated with the main air duct.

[0011] In the aforementioned external preheater system that uses superheated steam to increase the temperature of the boiler hot air, it is preferred that the straight-tube steam and air heat exchange device includes a heat exchange steam branch pipe that is arranged in a circle, and the inner diameter of the heat exchange steam branch pipe is equal to the outer diameter of the main air pipe; and the length section of the heat exchange steam branch pipe is covered by a tubular steam drum chamber and is connected to the main air pipe as a whole.

[0012] In the aforementioned external preheater system that utilizes superheated steam to increase the temperature of the hot air from the boiler, preferably, the heat exchange steam branch pipe is provided with fins toward the center of the circle formed therein.

[0013] In the aforementioned external preheater system that utilizes superheated steam to increase the temperature of the boiler hot air, preferably, the straight tube steam and air heat exchange device includes a steam core tube located in the center of the tubular steam drum chamber, and fins are provided on the circumference of the steam core tube; and the difference between the cross-section of the inner hole of the tubular steam drum chamber and the cross-section of the steam core tube is equal to the cross-section of the main air duct.

[0014] In the aforementioned external preheater system that utilizes superheated steam to increase the temperature of the boiler hot air, preferably, isolation valves are provided at both the steam inlet pipe and the air inlet pipe of the preheater.

[0015] In the aforementioned external preheater system that utilizes superheated steam to increase the temperature of the boiler hot air, preferably, an isolation valve is provided in the pipeline from the preheater to the gas supply main pipe.

[0016] This technical solution can be designed in an existing boiler power generation system, wherein the superheater and air preheater are installed in the flue, maintaining the characteristic of fully utilizing the flue waste heat. While the superheater output pipe normally supplies steam to the turbine, it does not affect the shutdown and start-up of the boiler drain. An independent external steam preheater is added using the pipeline drain pipe, and the air preheater output pipe is connected to the steam preheater, so that the primary air and superheated steam are heat exchanged in the steam preheater and then transported to the boiler air inlet. The steam pipe output from the steam preheater is then connected to the gas supply main pipe.

[0017] The pre-evaporator of this system is a heat exchange device independent of other heat exchange systems. It can be controlled and maintained independently, and the throughput can be adjusted according to the system air temperature and steam temperature. It has no external energy consumption.

[0018] Furthermore, the air preheater is connected to the primary air fan. Usually, the output temperature of the primary air is around 170°C. According to the principle of this device, the primary air will exchange heat with the steam in the preheater. Since the steam temperature after drainage is generally maintained at around 400°C, there is a large temperature difference with the primary air. The following purpose can be fully achieved through the design of physical conditions such as heat exchange time, heat exchange tube length, area, etc.: that is, to ensure that the steam temperature transported to the gas supply main pipe is at the requirement of 300°C, and the excess 100°C heat is added to the primary air.

[0019] This solution is further implemented through the following means: pressure gauges and thermometers are installed at the input and output pipes of the pre-steamer to control the specific data of the internal heat exchange. At the same time, the pre-steamer as a whole is preferably a straight-tube steam and air heat exchange device connected to the main air duct, ensuring that the air and steam operate under the originally designed fluid dynamic parameters. There are several ways to perform this straight-tube heat exchange. The steam pipe composed of the heat exchange steam branch pipe surrounds the air pipe, and the flow area of ​​the air pipe is equal to that of the main air duct; or the steam pipe is centered and conducts heat exchange outward. Of course, the difference between the cross-section of the inner hole of the tubular steam drum and the cross-section of the steam core pipe is equal to the cross-section of the main air duct, so that the air duct parameters are basically unaffected.

[0020] Compared with the prior art, the beneficial effects of the present invention are: using superheated steam to connect an independent pre-steamer through a drain pipe, the excess steam heat is converted to the primary air, thereby increasing the primary air temperature, improving the boiler combustion conditions, and greatly improving the combustion degree. Without the need for its own energy consumption, it not only meets the external steam supply requirements but also improves the boiler efficiency. It has a simple structure, a small amount of installation and modification work, and the air duct parameters are not affected. It is easy to control when connected to the entire system, and saves energy significantly. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0022] Figure 2It is a schematic diagram of the heat exchange structure of the steam and air ducts of a preheater of the present invention.

[0023] Figure 3 It is a structural schematic diagram of one embodiment of the cross-section arrangement of a steam and air duct of the present invention.

[0024] Figure 4 This is a structural schematic diagram of a second embodiment of the steam and air duct cross-section arrangement of the present invention.

[0025] In the figure: 1. Boiler, 2. Steam drum, 3. Steam preheater, 301. Tubular steam drum chamber, 302. Heat exchange steam branch pipe, 302a. Steam core pipe, 303. Main air duct, 4. Steam trap, 5. Superheater, 6. Air preheater, 7. Primary fan, 8. Flue induced draft fan, 9. Air supply main pipe, 10. Flue, 11. Steam trap header. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0027] See also Figure 1 This embodiment provides an external preheater system for increasing the temperature of boiler hot air by using superheated steam, including a boiler 1, a steam drum 2, a flue 10, a flue induced draft fan 8, and other infrastructure. A superheater 5 and an air preheater 6 are arranged in the flue 10. The input pipe of the superheater 6 is connected to the boiler steam drum 2. A steam trap 4 is provided at the output pipe of the superheater 6. The output from the superheater drain pipe is divided into two paths, one path entering a steam trap header 11, and the other path connecting to a preheater 3 independent of other heat exchange systems.

[0028] The pre-steamer 3 is a straight pipe steam and air heat exchange device connected to the main air duct 303. Figure 2 As shown, the main air duct 303 is connected to the air preheater 6, which is supplied with air by the primary fan 7. The air duct from the air preheater 6 is fed into the preheater 3, where it is transported to the boiler 1 inlet air after heat exchange between steam and air, further heating the primary air temperature. The steam pipe output from the preheater 3 is then connected to the main air supply pipe 9.

[0029] Pressure gauges and thermometers are provided on the steam input pipe and output pipe, and the air input pipe and output pipe of the pre-steamer 3; isolation valves are provided on the steam input pipe and air input pipe of the pre-steamer 3; and an isolation valve is provided in the pipeline from the pre-steamer 3 to the gas supply main pipe 9.

[0030] The straight tube heat exchange device of the pre-evaporator 3 is of a certain length determined according to actual conditions, and is designed based on the heat exchange principle using a straight tube structure arranged inside and outside.

[0031] Steam preheater 3 structure embodiment 1: straight tube steam, air heat exchange device includes 12 heat exchange steam branch pipes 302 arranged in a circle, such as Figure 3 As shown, the inner diameter (internal hole) of the twelve heat exchange steam branch pipes 302 is equal to the outer diameter of the main air duct 303. When the twelve heat exchange steam branch pipes 302 form a circle, a 5-10 cm gap is maintained between each pipe. Each heat exchange steam branch pipe 302 is equipped with fins toward the center of the circle. The fins are aligned with the air flow direction, which does not increase air resistance and ensures that each pipe receives sufficient heat exchange. The heat exchange steam branch pipes 302 are enclosed by the tubular steam drum chamber 301 and are integrally connected to the main air duct 303. The entire preheater 3 tube body is covered with insulation material.

[0032] Example 2 of the structure of the pre-steamer 3: It is also designed as a long straight tube structure for steam and air heat exchange. The difference from Example 1 is that the steam core tube 302a is arranged in the center of the tubular steam drum chamber 301, and heat dissipation fins are provided on the circumferential surface of the steam core tube 302a. The direction of the heat dissipation fins is also arranged along the direction of air flow. The difference between the cross-section of the inner hole of the tubular steam drum chamber 301 and the cross-section of the steam core tube 302a is equal to the cross-section of the main air duct 303, that is, the original air volume parameter requirements of the main air duct 303 are guaranteed. The outside of the entire pre-steamer 3 tube body is covered with thermal insulation material.

[0033] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any method, process, structure, etc. that is a simple transformation of the present invention falls within the scope of protection of the present invention.

Claims

1. An external steam preheater system for increasing the temperature of hot air from a boiler by using superheated steam, comprising a superheater (5) and an air preheater (6) located in a flue (10), characterized in that The superheater input pipe is connected to the boiler drum (2), and a steam trap (4) is provided at the superheater output pipe. The steam is output from the superheater drain pipe in two ways, one way entering the drain header (11) and the other way entering the preheater (3). At the same time, the air preheater output pipe passes through the preheater and then is delivered to the boiler (1) for air intake, so that the primary air temperature is further heated. The steam pipe output from the preheater is connected to the air supply main pipe (9). The pre-evaporator is a heat exchange device independent of other heat exchange systems; pressure gauges and thermometers are installed on the steam input and output pipes, and air input and output pipes of the pre-evaporator, as well as isolation valves; The pre-steamer (3) includes a straight-tube steam and air heat exchange device connected to the main air duct (303) as an integral whole; the straight-tube steam and air heat exchange device includes a heat exchange steam branch pipe (302) arranged in a circle, the inner diameter of the heat exchange steam branch pipe being equal to the outer diameter of the main air duct (303); and a length section of the heat exchange steam branch pipe is covered by a tubular steam drum chamber (301) and connected to the main air duct as an integral whole.

2. The external preheater system for increasing the temperature of boiler hot air by using superheated steam according to claim 1 is characterized in that: The air preheater (6) is connected to the primary air blower (7).

3. The external preheater system for increasing the temperature of boiler hot air by using superheated steam according to claim 1, characterized in that: The heat exchange steam branch pipe (302) is provided with fins toward the center of the circle formed.

4. The external preheater system for increasing the temperature of boiler hot air by using superheated steam according to claim 1, characterized in that: The straight tube steam and air heat exchange device comprises a steam core tube (302a) located at the center of a tubular steam drum chamber (301), with fins provided on the circumference of the steam core tube; and the difference between the cross section of the inner hole of the tubular steam drum chamber and the cross section of the steam core tube is equal to the cross section of the main air duct (303).

5. The external preheater system for increasing the temperature of boiler hot air by using superheated steam according to claim 1 is characterized in that: An isolation valve is provided in the pipeline from the pre-steamer (3) to the gas supply main pipe (9).

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