CN105526599B - The upgrading of clean type coal-burning boiler smoke discharging residual heat utilizes system - Google Patents

Abstract

The invention belongs to the technical field of power station energy-saving equipment design, and in particular relates to a clean coal-fired boiler smoke waste heat improvement utilization system, in which a furnace 10, a superheater 11, a reheater 12, and an economizer 13 are sequentially connected in the boiler; Economizer 13 is connected to air preheater 1 through air preheater inlet flue 8; primary fan 2 is connected to air preheater 1 through air preheater inlet duct 3 in turn, and air preheater outlet duct 4 Pass through the hot primary air duct 5 in turn, and the pulverizing system is connected to the furnace; the hot primary air bypass 6 is installed on the outlet air duct 4 of the air preheater, and a bypass induced draft fan 7 is installed on the hot primary air bypass 6 to keep the hot air Pressure head, and a bypass hot air heat exchanger group 14 connected to the demanded energy cooling source 15 is arranged on the hot primary air bypass 6; the outlet of the hot primary air bypass 6 is connected to the inlet air duct 3 of the air preheater. The invention effectively utilizes the exhaust heat of the boiler and improves the utilization efficiency of energy.

Description

Clean Coal-fired Boiler Exhaust Heat Quality Improvement Utilization System

technical field

The invention belongs to the technical field of power station energy-saving equipment design, and in particular relates to a clean coal-fired boiler smoke waste heat improvement utilization system.

Background technique

According to the first law of thermodynamics, due to the huge mass flow rate of the exhaust gas, the heat loss of the exhaust gas of the coal-fired boiler is a large specific gravity energy loss of the boiler. At present, the design value of the exhaust gas temperature of domestic mainstream large-capacity units is about 120°C, but in actual operation, the phenomenon of exhaust gas overheating is very common, and some lignite boilers can even reach about 160°C. Compared with the acid dew point generally at 80-90°C, there is still room for further utilization of flue gas waste heat.

At present, the commonly used waste heat utilization method is to introduce the condensed water in the steam-water system of the steam turbine into the exhaust flue after the air preheater, and directly use the waste heat of the flue gas to heat the condensed water. This utilization method is simple in principle, and can effectively squeeze out the extraction steam of the low-pressure cylinder and reduce the heat consumption of the steam turbine.

Although traditional waste heat utilization is simple and effective, from the perspective of the second law of thermodynamics, smoke exhaust, as a low-grade heat source with a temperature far below 200°C, has very limited work ability, which is also the root cause of the limited actual energy saving level of traditional waste heat utilization. Specifically, the traditional waste heat utilization can only use the exhaust gas to heat the condensate system, and the steam extraction efficiency of the condensate part is low, so the energy saving capacity is limited. Therefore, in recent years, some technical solutions for the utilization of exhaust waste heat after upgrading the energy level have been produced. For example, Sun Fengzhong invented a multi-stage utilization system for power station boiler exhaust heat energy transfer. After recognizing the limitations of smoke exhaust, it is no longer satisfied. For the direct application of exhaust heat. This heat utilization method essentially transfers the exhaust waste heat to a higher-parameter heat-carrying working medium, and then performs heat utilization for the heat-carrying working medium. The upgraded flue gas waste heat can heat the water supply system of the steam turbine and squeeze out the extraction steam with higher parameters, thus bringing about lower energy consumption for power generation.

In addition, the direct utilization of flue gas waste heat has inherent disadvantages: first, the heat transfer limit of flue gas is basically determined by the acid dew point, further reducing the heat transfer limit requires special materials or special technologies; Dust may cause dust accumulation and wear of the heat exchanger. Long-term use will reduce the heat transfer capacity and affect the life of the heat exchanger. Regular maintenance and timely replacement of relevant pipelines are required. These problems are unavoidable in traditional exhaust waste heat utilization.

The current mainstream air preheater often has the problem of cold end to be optimized. The inlet temperature of the cold primary air of the air preheater without a heater is generally around 30°C, while the exhaust gas temperature is usually around 120°C or above, which makes the heat transfer of the air preheater The loss is at a relatively high level, not to mention the obvious improvement of the unit such as "mixed cold air". Common air preheater hot end temperature adjustment measures that are damaged. At present, many energy-saving measures consider energy utilization other than conventional heat exchangers of boilers, but energy-saving optimization based on the second law of thermodynamics for traditional heat exchangers is rare.

Contents of the invention

In order to recover exhaust waste heat by matching the energy level of the cold end of the air preheater, improve its energy level and utilize it, so as to solve the heat exchange problem of the air preheater in the prior art Excessive loss, excessive exhaust smoke temperature, limited application of waste heat, and low-temperature corrosion, wear, and dust accumulation in the utilization process. The present invention proposes a clean coal-fired boiler exhaust heat improvement utilization system, including:

Furnace 10, superheater 11, reheater 12, and economizer 13 are sequentially connected in the boiler; economizer 13 is connected to air preheater 1 through air preheater inlet flue 8, and air preheater outlet flue Road 9 is connected to the electrostatic precipitator;

The primary fan 2 is connected to the air preheater 1 through the air preheater inlet duct 3 in turn, and the air preheater outlet duct 4 is connected to the furnace through the hot primary air duct 5 and the pulverizing system in turn;

A hot primary air bypass 6 is arranged on the outlet duct 4 of the air preheater, and a bypass induced draft fan 7 is installed on the hot primary air bypass 6 to keep the hot air pressure head, and is arranged on the hot primary air bypass 6 to meet the demand. The bypass hot air heat exchanger group 14 connected to the energy supply cold source 15; the outlet of the hot primary air bypass 6 is connected to the inlet air duct 3 of the air preheater.

The principle of the control system of the invention is simple, effectively utilizes the exhaust heat of the boiler, and improves the energy utilization efficiency through the re-matching of the heat source and the cold source in the unit, and can effectively improve the economic benefit of the power station.

Description of drawings

Figure 1 is a schematic diagram of the core components of the clean coal-fired boiler exhaust heat improvement utilization system;

Figure 2 is a structural diagram of a clean coal-fired boiler exhaust heat improvement utilization system. The labels in the figure respectively indicate: 1-air preheater; 2-primary fan; 3-inlet air duct of air preheater; 4-outlet air duct of air preheater; 5-hot primary air duct; 6-hot primary air Bypass; 7-bypass induced draft fan; 8-air preheater inlet flue; 9-air preheater outlet flue; 10-furnace; 11-superheater; 12-reheater; 13-economizer ;14-Bypass hot air heat exchanger group; 15-Required energy supply cold source; 16-Turbine steam-water system assembly; 17-Steam turbine high-pressure cylinder; 18-Steam turbine medium-pressure cylinder; 19-Steam turbine low-pressure cylinder; 20-Generator ;21-condenser; 22-feedwater pump drives steam turbine; 23-condensate pump; 24-deaerator; 25-feedwater pump; 26-first high-pressure heater; 27-second high-pressure heater; 28-third High-pressure heater; 29-first low-pressure heater; 30-second low-pressure heater; 31-third low-pressure heater; 32-fourth low-pressure heater; 33-first-stage air-water heat exchanger; 34-second 35-the fourth valve; 36-the third valve; 37-the second valve; 38-the first valve.

Detailed ways

The embodiments will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the present invention proposes a clean coal-fired boiler flue gas waste heat improvement utilization system, including:

Furnace 10, superheater 11, reheater 12, and economizer 13 are sequentially connected in the boiler; economizer 13 is connected to air preheater 1 through air preheater inlet flue 8, and air preheater outlet flue Road 9 is connected to the electrostatic precipitator;

The primary fan 2 is connected to the air preheater 1 through the air preheater inlet duct 3 in turn, and the air preheater outlet duct 4 is connected to the furnace through the hot primary air duct 5 and the pulverizing system in turn;

A hot primary air bypass 6 is arranged on the outlet duct 4 of the air preheater, and a bypass induced draft fan 7 is installed on the hot primary air bypass 6 to keep the hot air pressure head, and is arranged on the hot primary air bypass 6 to meet the demand. The bypass hot air heat exchanger group 14 connected to the energy supply cold source 15; the outlet of the hot primary air bypass 6 is connected to the inlet air duct 3 of the air preheater.

The first high-pressure heater 26 and the second high-pressure heater 27 are respectively connected to the high-pressure cylinder 17 of the steam turbine;

The third high-pressure heater 28 and the deaerator 24 are respectively connected to the medium-pressure cylinder 18 of the steam turbine;

The first low-pressure heater 29, the second low-pressure heater 30, the third low-pressure heater 31, the fourth low-pressure heater 32 and the condenser 21 are connected to the steam turbine low-pressure cylinder 19 respectively;

Economizer 13, first high pressure heater 26, second high pressure heater 27, third high pressure heater 28, deaerator 24, first low pressure heater 29, second low pressure heater 30, third low pressure heater 31. The fourth low-pressure heater 32 is connected to the condenser 21 in sequence;

The inlet of the first-stage wind-water heat exchanger 33 is connected with the inlet of the third high-pressure heater 28 through the third valve 36, and the outlet of the first-stage wind-water heat exchanger 33 is connected with the second high-pressure heater 27 through the fourth valve 35. connected to the exit.

The inlet of the second-stage wind-water heat exchanger 34 is connected with the inlet of the fourth low-pressure heater 32 through the first valve 38, and the outlet of the second-stage wind-water heat exchanger 34 is connected with the second low-pressure heater 30 through the second valve 37. connected to the exit.

The air outlet of the second-stage wind-water heat exchanger 34 is connected with the cold primary air duct.

The bypass induced draft fan 7 controls the wind pressure of the hot primary air bypass 6 to be higher than the wind pressure of the air preheater outlet duct 4 and lower than the outlet wind pressure of the primary fan 2 .

In existing power plant equipment, three-stage high-pressure heaters (26, 27, 28), one-stage deaerator (24) and four-stage low-pressure heaters (29, 30, 31, 32) are generally used to extract steam from the steam turbine To heat the condensed water in the system, this part of the steam leaves the steam turbine cylinder and will not be able to continue to do work, but the steam extraction can also increase the temperature of the feed water, and at the same time reduce the heat transfer temperature difference of the relevant heat exchange surfaces of the boiler, which can reduce the boiler’s temperature. heat transfer damage, but also helps to improve the operating safety of the unit. In fact, if there are other matching heat sources in the unit to replace the extracted steam to heat a part of the condensed water, the corresponding proportion of the steam extracted by the steam turbine can be reduced, and this part of the steam can do further work in the cylinder. If the use of this heat source does not add additional energy consumption to the unit, it can be considered that the unit has obtained higher power generation under the same energy consumption, that is, the economic efficiency of the unit has been improved.

The working method of the present invention is: the 300-350°C hot air from the outlet duct 4 of the air preheater is divided into two parts, one part enters the primary air duct 5 of the boiler and flows into the furnace after passing through the pulverizing system; the other part enters the bypass air duct 6 and flow through the first-stage air-water heat exchanger 33 and the second-stage air-water heat exchanger 34 in turn, then mix with the cold primary air after the primary fan 2, enter the air preheater 1, and continue the above cycle after heat exchange .

The third valve 36 and the fourth valve 35 have played a role in controlling the feedwater position and its flow rate entering the first-stage wind-water heat exchanger 33, and can utilize the first-stage wind-water heat exchanger 33 to recover heat from bypass hot air to heat part of the feedwater, reducing the The steam extraction volumes of the second high-pressure heater 27 and the third high-pressure heater 28 exclude the steam extraction of the steam turbine with higher steam extraction efficiency.

In the same way, the first valve 38 and the second valve 37 play a role in controlling the position and flow of the feed water entering the second-stage air-water heat exchanger 34, and the second-stage air-water heat exchanger 34 can be used to recover the heat of the bypass hot air to heat part of the condensation water, reducing the steam turbine extraction volume of the second low-pressure heater 30, the third low-pressure heater 31, and the fourth low-pressure heater 32, which can also achieve a certain energy-saving effect. At the same time, due to the use of the first-stage wind-water heat exchanger 33, the temperature matching of the working medium at the second-stage wind-water heat exchanger 34 is higher. According to the second law of thermodynamics, unnecessary thermal energy depreciation can be avoided.

Compared with the traditional waste heat utilization technology, the technical effects brought by the present invention are:

1. It can effectively utilize the exhaust waste heat, and improve the working environment of the waste heat utilization equipment, which can improve the thermal economy and operation safety of the unit. Compared with the traditional smoke exhaust waste heat utilization scheme, due to the improvement of the energy level, although the first law of thermodynamics has the same heat transfer rate, the hot air in this scheme can squeeze out the steam turbine with higher steam extraction efficiency, and the working capacity is stronger , can achieve a significant improvement in thermal economy.

2. High matching of energy levels has positive significance to the energy saving level of the unit. according to According to the analysis theory, the temperature of the hot primary air and exhaust gas can be controlled and the preheating of the cold primary air can greatly reduce the heat transfer of the air preheater system loss; and the reasonable use of heat from the bypass heat primary air can directly reduce the heat consumption of the steam turbine. On the whole, the temperature matching degree of the working fluid in this scheme is higher, which is more conducive to the improvement of the thermal economy of the unit.

3. It can effectively reduce and flexibly control the temperature of the hot primary air, improve the operation safety of the milling system, and effectively alleviate or even eliminate the need for "mixing cold air".

4. It can effectively alleviate the phenomenon of overheating of the exhaust gas of the lignite unit.

5. It can effectively solve the problems of low-temperature corrosion, wear and dust accumulation on the heating surface of the tail.

6. The system is simple and easy to implement, with limited investment requirements; the output is flexible and easy to adapt to local conditions.

This embodiment is only a preferred specific implementation of the present invention, but the scope of protection of the present invention is not limited thereto, any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention , should be covered within the protection scope of the present invention.

Claims (1)

1. a kind of clean type coal-burning boiler smoke discharging residual heat upgrading utilizes system, which is characterized in that including：It is sequentially connected in boiler Burner hearth (10), superheater (11), reheater (12), economizer (13)；Economizer (13) passes through air preheater gas approach (8) it is connected with air preheater (1), air preheater exhaust pass (9) is connected with electric dust-removing equipment；

Primary air fan (2) passes sequentially through air preheater inlet conduits (3) and is connected with air preheater (1), and air preheater goes out One's intention as revealed in what one says road (4) passes sequentially through heat primary air road (5), pulverized coal preparation system is connected with burner hearth；

On air preheater outlet conduits (4) heat primary air is set to bypass (6), install bypass air inducing in heat primary air bypass (6) additional Machine (7) keeps hot wind pressure head, and arrangement exchanges heat with that need to energize the gas bypass that low-temperature receiver (15) is connected in heat primary air bypass (6) Device group (14)；The outlet access air preheater inlet conduits (3) of heat primary air bypass (6)；

First high-pressure heater (26), the second high-pressure heater (27) are connected respectively with steam turbine high-pressure cylinder (17)；

3rd high-pressure heater (28), oxygen-eliminating device (24) are connected respectively with Steam Turbine Through IP Admission (18)；

First low-pressure heater (29), the second low-pressure heater (30), the 3rd low-pressure heater (31), the 4th low-pressure heater (32) it is connected respectively with turbine low pressure cylinder (19) with condenser (21)；

Economizer (13), the first high-pressure heater (26), the second high-pressure heater (27), the 3rd high-pressure heater (28), deoxygenation Device (24), the first low-pressure heater (29), the second low-pressure heater (30), the 3rd low-pressure heater (31), the 4th low-pressure heating Device (32) and condenser (21) are sequentially connected；

The import of first order geomantic omen heat exchanger (33) is connected by the 3rd valve (36) with the entrance of the 3rd high-pressure heater (28), The outlet of first order geomantic omen heat exchanger (33) is connected by the 4th valve (35) with the outlet of the second high-pressure heater (27)；

The import of second level geomantic omen heat exchanger (34) is connected by the first valve (38) with the entrance of the 4th low-pressure heater (32), The outlet of second level geomantic omen heat exchanger (34) is connected by the second valve (37) with the outlet of the second low-pressure heater (30)；

The air outlet slit of second level geomantic omen heat exchanger (34) is connected with a cold air passage；

The bypass air-introduced machine (7) controls the wind pressure of heat primary air bypass (6) to be higher than the wind pressure of air preheater outlet conduits (4) And less than the outlet wind pressure of primary air fan (2)；

The working method of the system：The 300-350 DEG C of hot wind from air preheater outlet conduits (4) is divided into two parts, and one Part enters burner hearth after flowing through pulverized coal preparation system into boiler heat primary air road (5)；Another part enters heat primary air bypass (6) simultaneously Followed by first order geomantic omen heat exchanger (33) and second level geomantic omen heat exchanger (34), then with cold one after primary air fan (2) Secondary wind mixing, into air preheater (1), continues above-mentioned cyclic process after heat exchange；

3rd valve (36) and the 4th valve (35) play control into first order geomantic omen heat exchanger (33) feedwater position and Using the heat part feedwater of first order geomantic omen heat exchanger (33) recycling gas bypass, it is high to reduce second for its flow The extraction flow of steam of heater (27) and the 3rd high-pressure heater (28) is pressed, has squeezed the more efficient steam turbine of steam extraction and has taken out Vapour；

First valve (38) and the second valve (37) play control into second level geomantic omen heat exchanger (34) feedwater position and Its flow using a part of condensation water of heat of second level geomantic omen heat exchanger (34) recycling gas bypass, reduces second Low-pressure heater (30), the 3rd low-pressure heater (31), the extraction flow of steam of the 4th low-pressure heater (32), are realized certain Energy-saving effect.