CN106895390A - A kind of station boiler multi-element heterogeneous afterheat utilizing system - Google Patents

Abstract

The invention discloses a multi-element and heterogeneous waste heat utilization system for power station boilers. According to the flow direction of the flue gas, a flue gas bypass is also arranged between the flue gas inlet end and the flue gas outlet end of the air preheater, and the flue gas bypass is sequentially arranged. A bypass high-pressure economizer and a bypass low-pressure economizer are connected in series; according to the air flow direction, the inlet port of the air preheater also passes through the primary cold air and the secondary cold air, and the primary cold air passes through the air preheater and heats the primary air in turn. The air cooler is then combined with another primary air cooling channel and then passed into the coal mill; the secondary cold air is preheated by the air preheater and partly sent to the furnace, and the other part flows through the hot air slag cooler and then sent to the furnace; According to the discharge direction of the slag, the system also includes a hot air slag cooler and a low temperature water cooled slag device connected in series. Part of the secondary cold air is sent to the furnace; the low-temperature water-cooled slag device is connected in parallel with the bypass low-pressure economizer.

Description

A Multivariate and Heterogeneous Waste Heat Utilization System for Power Plant Boilers

technical field

The invention belongs to the technical field of energy and power, and in particular relates to a multiple heterogeneous waste heat utilization system of a utility boiler.

Background technique

At present, there are many waste heat resources of power plant boilers in my country, but only the waste heat of boiler flue gas has been utilized as a resource. There are still many waste heat resources that are not being utilized.

Refer to Figure 1 for the boiler air-smoke system without waste heat. The flue gas generated by boiler combustion flows through the furnace (1), air preheater (2), dust collector (3) and induced draft fan (4) to the desulfurization system at one time. The cold air from the blower (5) directly enters the furnace of the boiler through the air preheater heater, and the cold air from the primary fan (6) is divided into two paths, one path becomes hot air after being heated by the air preheater (2), and the other path passes through the cold air door (7) After adjustment, it will reach a suitable temperature with the first round, and then enter the furnace through the coal mill (8).

The temperature of the primary air at the outlet of the coal mill (8) must be in a suitable temperature range, which varies according to the coal quality and the coal mill. If the temperature is too high, the possibility of pulverized coal explosion will increase greatly, and the safety of power plant operation will be seriously threatened; if the temperature is too low, the moisture in the coal will not completely evaporate and become liquid, which will easily lead to blockage of the powder pipe at the outlet of the coal mill. Therefore, modern power plants generally adjust the inlet air temperature of the coal mill through the opening of the cold air door (7) to achieve the purpose of controlling the outlet temperature of the coal mill.

1. Boiler exhaust heat

The exhaust gas temperature of the boiler is generally above 120°C, and the heat loss of the exhaust gas accounts for 70-80% of the heat loss of the boiler. Wind and cold secondary air, the flue gas temperature at the outlet of the air preheater will increase accordingly. For this reason, the method shown in Figure 2 adds an air preheater bypass flue, and a bypass high-pressure economizer is installed in the bypass flue to replace part of the high-pressure heater, and the energy saving is relatively high. But it will cause the temperature of the secondary hot air to decrease, and the energy saving effect is low.

2. Heat primary air waste heat

It has been explained before that in order to keep the outlet of the coal mill (8) in a suitable temperature range, the temperature of the air entering the coal mill (8) is adjusted through the cold air door (7). During normal operation, the temperature of the hot primary air is about 300°C, and the temperature entering the coal mill (8) after mixing is about 200°C. The hot primary air drops from 300°C to 200°C to release part of the heat, which is directly wasted.

The existing method of utilizing the heat of the hot primary air is: cancel the cold air door (7), and all the cold primary air enters the air preheater (2). On the hot primary air pipe at the outlet of the air preheater (2), the condensed water of the steam turbine recovery system is heated to replace part of the low heating. Under the premise of keeping the coal consumption unchanged, the power generation capacity will be increased.

The disadvantages of the above-mentioned hot primary air utilization system are: first, the total air volume entering the air preheater increases, resulting in a drop in the temperature of the hot secondary air, which affects the energy saving of the system; second, the heat transfer temperature difference of the hot primary air cooler If it is too large, adjusting the condensate flow into the hot primary air cooler has limited influence on adjusting the outlet air temperature of the coal mill.

3. Boiler slag waste heat

In power plant pulverized coal boilers, 90% of the ash in the coal is turned into fly ash after combustion, and is discharged from the chimney along with the flue gas. The remaining 10% becomes slag and is discharged from the cold ash hopper of the boiler. The temperature of the slag is very high, around 1000°C. Power plants generally use liquid slag discharge furnaces. The high temperature slag falls directly into the pool below the cold ash hopper to cool down. After wasting a lot of heat, it is discharged by the slag extractor.

Due to the different temperature levels of the three waste heat resources of flue gas, hot primary air waste heat and slag waste heat, there is currently no system that comprehensively considers the above three waste heat resources to optimize the thermal system and improve the economy of the thermal system. Aiming at this problem, the present invention proposes a multi-element and heterogeneous waste heat utilization system for thermal power plant boilers. The so-called multiple means that three or more waste heat resources are considered. The so-called heterogeneity means that each kind of waste heat has different temperature grades.

Contents of the invention

In view of the above problems, the object of the present invention is to propose a multiple heterogeneous waste heat utilization system for utility boilers. The invention comprehensively considers the above three waste heat resources, optimizes the thermal system, and improves the economical efficiency of the thermal system.

The invention provides the first multi-element and heterogeneous waste heat utilization system for power plant boilers.

The first multi-element and heterogeneous waste heat utilization system for utility boilers includes air preheaters, dust collectors, induced draft fans and flue gas coolers connected in series according to the flue gas flow direction; at the flue gas inlet end of the air preheater and There is also a flue gas bypass between the flue gas outlet ports, and the flue gas bypass is connected in series with a bypass high-pressure economizer and a bypass low-pressure economizer;

According to the direction of air circulation, the inlet of the air preheater is also fed with primary cold air and secondary cold air. The primary cold air passes through the air preheater and the hot primary air cooler in turn, and then merges with another primary air cooling channel and then enters the pulverized coal. machine; the secondary cold air is preheated by the air preheater and partly sent to the furnace, and part of it is sent to the furnace after being heated by the hot air slag cooler.

According to the discharge direction of the slag, the system also includes a hot air slag cooler and a low temperature water cooled slag cooler connected in series. Part of the secondary hot air is sent to the furnace; the low-temperature water-cooled slag device and the air preheater bypass low-pressure economizer are arranged in parallel.

Further, the air preheater is connected with the primary fan through the primary air heater, and the primary air heater is used to heat the primary cold air sent by the primary fan; the air preheater is connected with the blower through the secondary air heater, The secondary air heater is used for heating the secondary cold air delivered by the blower.

Further, the flue gas cooler is respectively connected with the primary air heater and the secondary air heater through the closed circulating water system;

Further, the bypass high-pressure economizer and bypass low-pressure economizer are respectively connected in parallel with the high-pressure heater and the low-pressure heater.

The invention provides the second multi-element and heterogeneous waste heat utilization system for utility boilers.

The second multivariate and heterogeneous waste heat utilization system for utility boilers is characterized in that, according to the flue gas flow direction, it includes an air preheater, a dust collector, an induced draft fan and a flue gas cooler connected in series in sequence; the flue gas cooler in the air preheater There is also a flue gas bypass between the gas inlet port and the flue gas outlet port, and the flue gas bypass is connected in series with a bypass high-pressure economizer and a bypass low-pressure economizer;

According to the direction of air circulation, the inlet of the air preheater is also fed with primary cold air and secondary cold air. The primary cold air passes through the air preheater and the hot primary air cooler in turn, and then merges with another primary air cooling channel and then enters the pulverized coal. machine; the secondary cold air is preheated by the air preheater and partly sent to the furnace, and part of it is sent to the furnace after being heated by the hot air slag cooler.

According to the direction of slag discharge, the system also includes a low-temperature water-cooled slag device and a high-temperature water-cooled slag device connected in series. The high-temperature water-cooled slag device is directly installed at the bottom of the furnace. .

Further, the air preheater is connected with the primary fan through the primary air heater, and the primary air heater is used to heat the primary cold air sent by the primary fan; the air preheater is connected with the blower through the secondary air heater connected, the secondary air heater is used to heat the secondary cold air delivered by the blower.

Further, the flue gas cooler communicates with the primary air heater and the secondary air heater respectively through a closed circulating water system;

Further, the bypass high-pressure economizer and bypass low-pressure economizer are respectively connected in parallel with the high-pressure heater and the low-pressure heater.

The invention provides a third multi-element and heterogeneous waste heat utilization system for power plant boilers.

The third multivariate and heterogeneous waste heat utilization system for utility boilers is characterized in that, according to the flow direction of the flue gas, it includes an air preheater, a dust collector, an induced draft fan and a flue gas cooler connected in series in sequence; There is also a flue gas bypass between the gas inlet port and the flue gas outlet port, and the flue gas bypass is connected in series with a bypass high-pressure economizer and a bypass low-pressure economizer;

According to the direction of air circulation, the inlet of the air preheater is also fed with primary cold air and secondary cold air. The primary cold air passes through the air preheater and the hot primary air cooler in turn, and then merges with another primary air cooling channel and then enters the pulverized coal. machine; the secondary cold air is preheated by the air preheater and partly sent to the furnace, and part of it is sent to the furnace after being heated by the hot air slag cooler.

According to the discharge direction of the slag, the system also includes a hot air slag cooler and a low temperature air cooled slag device connected in series. Part of the secondary hot air is sent to the furnace; the secondary cold air heated by the closed water system is sent to the air preheater through the low-temperature air-cooled slag device.

Further, the air preheater is directly connected with the primary fan, and the primary fan directly sends the primary cold air to the air preheater; the low-temperature air-cooled slag device is directly connected with the blower, and the blower directly sends the secondary cold air to the low-temperature air Slag cooler.

The beneficial effects of the present invention are:

(1) The present invention realizes cascaded utilization of hot primary air, flue gas and slag waste heat, and heats cold source working fluids with appropriate temperature according to the temperature levels of the three waste heat resources of hot primary air, flue gas and slag, such as: high temperature Wind, low-temperature wind, high-temperature water, and low-temperature water; considering the three waste heat resources of hot primary air, flue gas and slag, the thermal system is optimized and the economy of the thermal system is improved.

(2) The present invention utilizes bypass flue high-pressure economizer, bypass flue low-pressure economizer and hot primary air cooler equipment to heat the condensate or feed water of the steam turbine regenerating system to replace part of the high or low heating effect . On the premise that the amount of coal burned remains unchanged, the power generation and the economy of the unit are improved.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application.

Figure 1 is a schematic structural diagram of a power plant boiler system without waste heat utilization;

Fig. 2 is a schematic structural diagram of a power plant boiler system utilizing flue gas waste heat;

Fig. 3 is a structural schematic diagram of Embodiment 1 of a multi-element heterogeneous waste heat utilization system for a utility boiler;

Fig. 4 is a structural schematic diagram of Embodiment 2 of a multi-element heterogeneous waste heat utilization system for a utility boiler;

Fig. 5 is a structural schematic diagram of Embodiment 3 of a multi-element heterogeneous waste heat utilization system for a utility boiler;

Fig. 6 is a schematic structural diagram of Embodiment 4 of a multi-element heterogeneous waste heat utilization system for a utility boiler;

Fig. 7 is a schematic structural diagram of Embodiment 5 of a multi-element and heterogeneous waste heat utilization system for a utility boiler.

Among them, 1. furnace; 2. air preheater; 3. dust collector; 4. induced draft fan; 5. blower fan; 6. primary fan; 7. cold air door; 8. coal mill; , low-pressure heater; 11, feed water pump; 12, condensate pump; 13, flue gas cooler; 14, secondary air heater; 15, primary air heater; 16, bypass high-pressure economizer; 17, Bypass low-pressure economizer; 18. Hot air-cooled slag device; 19. Low-temperature water-cooled slag device; 20. Hot primary air cooler; 21. High-temperature water-cooled slag device; 22. Low-temperature air-cooled slag device.

detailed description

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

Implementation Case 1

Fig. 3 is a structural schematic diagram of Embodiment 1 of a multi-element and heterogeneous waste heat utilization system for a utility boiler.

As shown in Figure 3, the multiple heterogeneous waste heat utilization system of power plant boilers, according to the flue gas flow direction, includes air preheaters (2), dust collectors (3), induced draft fans (4) and flue gas coolers connected in series (13); a flue gas bypass is also arranged between the flue gas inlet port and the flue gas outlet port of the air preheater (2), and the bypass high-pressure economizer (16) and the bypass high pressure economizer (16) are connected in series successively on the flue gas bypass Bypass low pressure economizer (17);

According to the direction of air flow, the inlet port of the air preheater (2) also feeds primary cold air and secondary cold air. The primary air-cooled air is combined and fed into the coal mill (8); the secondary cold air is preheated by the air preheater (2) and partly sent to the furnace (1), and the other part is sent to the furnace after passing through the hot air slag cooler (18). Furnace (1);

According to the slag discharge direction, the system also includes a hot air slag cooler (18) and a low temperature water cooled slag cooler (19) connected in series, the hot air slag cooler (18) is directly installed at the bottom of the furnace (1), and the hot air slag cooler (18) also pass through the secondary cold air preheated by the air preheater (2) and then send it to the furnace (1); effect.

In this embodiment, the air preheater (2) is connected to the primary air blower (6) through the primary air heater (15), and the primary air heater (15) is used to heat the primary air blower (6). primary cold air; the air preheater (2) is connected to the blower (5) through the secondary air heater (14), and the secondary air heater (14) is used to heat the secondary air sent by the blower (5). Second cold wind.

The present invention utilizes the cold air door (7) to control the flow of the primary air entering the coal mill (8) from the primary fan (6).

The flue gas cooler (13) communicates with the primary air heater (14) and the secondary air heater (15) respectively through a closed circulating water system.

The bypass high-pressure economizer (16) and the bypass low-pressure economizer (17) are respectively connected in parallel with the high-pressure heater (9) and the low-pressure heater (10).

The present invention uses the bypass high-pressure economizer (16) and the bypass low-pressure economizer (17) to heat the condensate or feedwater of the steam turbine reheating system, replacing part of the high-fill or low-fill effect, so that the amount of coal burned remains unchanged Under the premise of improving the generating power and the economy of the unit.

Wherein, the condensate pump (12) is connected with the low pressure heater (10), and the feed water pump (11) is connected with the high pressure heater (9).

The following is a detailed description of the system in combination with the flue gas flow, air flow and slag flow in the multiple heterogeneous waste heat utilization system of the utility boiler:

Flue gas flow: The air preheater is equipped with a bypass flue, and the flue gas from the boiler is divided into two paths before entering the rotary air preheater (2). One way flows through the air preheater (2) to transfer the flue gas heat to the primary and secondary air; the other way flows through the bypass flue, where the bypass high pressure economizer (16) and the bypass low pressure ), the flue gas heat is transferred to part of the feed water and condensed water respectively, replacing part of the high-pressure heater (9) and the low-pressure heater (10). After the two paths of flue gas are combined, they respectively flow through the dust collector (3), the induced draft fan (4) and the flue gas cooler (13). In the flue gas cooler (13), the heat of the flue gas passes through the closed circulation water to heat the primary and secondary cold air.

Air flow: the primary and secondary air enters the primary air heater (15) and the secondary air heater (14) through the primary blower (6) and the blower (5) respectively, and the primary and secondary cold air is heated by waste heat from exhaust smoke. The heated primary and secondary air enters the rotary air preheater (2), and the hot primary air passes through the hot primary air cooler (20) to heat part of the feed water, replacing part of the high-pressure heater (9). The cooled hot primary air is mixed with the primary air from the primary blower through the bypass damper (7) to a suitable temperature and enters the coal mill (8). After the primary air powder mixture flows out from the coal mill (8), it directly enters the furnace. Part of the hot secondary air directly enters the furnace, and part of it is introduced into the high-temperature air-cooled slag device (18), and the hot secondary air is heated by using the waste heat of the high-temperature slag, and then sent into the furnace.

Condensate water process: water from the low-pressure part of the steam turbine reheating system (the specific lead-out position is different due to the actual situation of the unit), divided into two parallel connections. One way enters the bypass low-pressure economizer (17), and the other enters the low-temperature water-cooled slag vessel (19), absorbing the flue gas heat of the bypass flue gas of the preheater and the low-temperature waste heat of the slag respectively, and then converging and returning to the steam turbine condensate system (specifically The location of the return point is different due to the actual situation of the unit).

Water supply process: Two channels of water from the outlet of the feed water pump are connected in parallel, one channel enters the bypass high-pressure economizer (16), and the other channel enters the hot primary air cooler (20) to absorb the heat and heat of the air preheater bypass flue gas respectively. After the high temperature and residual heat of the primary air, they are combined and returned to the steam turbine water supply system.

Slag process: the high-temperature boiler slag is cooled through the high-temperature air-cooled slag device (18) and the low-temperature water-cooled slag device (19), and the heat of the high-temperature slag is transferred to the high-temperature air and low-temperature water before being discharged from the boiler.

Implementation Case 2

As shown in Figure 4, the main difference with embodiment one is that the high-temperature air-cooled slag device (18) is replaced by a high-temperature water-cooled slag device (21), and the high-temperature water-cooled slag device (21) is connected with the hot primary air cooler (20) and the bypass high-pressure economizer (16) are connected in parallel to heat the feed water from the outlet of the feed water pump (11), and the hot water at the outlet of the three parallel devices (16, 20, 21) is connected with the last-stage high-pressure heater (9 ) and the outlet water pipeline is connected to replace part of the high-pressure heater (9). The rest of the pipeline system is similar to the implementation case 1.

Implementation Case Three

As shown in Figure 5, the main difference from the first embodiment is that the low-temperature air-cooled slag container (22) is used instead of the low-temperature air-cooled slag container (19). The secondary air of the wind device (14) enters the rotary air preheater (2) after transferring the boiler low-temperature slag residual heat to the secondary air. Other piping systems are similar to the implementation case 1.

Implementation Case 4

As shown in Figure 6, the main difference from the previous three implementation cases is that the heating method of the air at the inlet of the air preheater is different. and the closed circulating water system composed of the secondary air heater (15) utilizes the waste heat of the flue gas to heat the cold air from the primary fan (6) and the blower fan (5).

The air heating mode of this case is: from the cold wind of blower fan (5), at first flow through low-temperature air-cooled slag device (22) and raise wind temperature. Then it is divided into two paths, one path directly enters the rotary air preheater (2) as the secondary air, and the other path enters the rotary air preheater (2) after the primary fan (6) is set to lift the pressure head.

Due to the cancellation of the closed circulation system, the system does not set the primary air heater (15) and the secondary air heater (14), the flue gas cooler (13) and the bypass low-pressure economizer (17) Parallel connection, heating the condensed water from the outlet of a certain stage low-pressure heater (10) of the steam turbine, the outlet hot water of the two parallel devices (13, 17) is connected with the outlet water pipeline of the other stage low-pressure heater (10), replacing part The effect of low plus plus (10). The rest of the system is similar to the third implementation case.

Implementation Case Five

As shown in Figure 7, the implementation case five is a simplified version of the implementation case four, which can reduce part of the investment and achieve a slightly lower energy saving effect than the implementation case five. The main difference from the fourth implementation case is that the bypass flue of the air preheater (2), the bypass high-pressure economizer (16) and the bypass low-pressure economizer (17) are cancelled. The hot primary air cooler (20) is used to replace part of the high-pressure heater (9), and the flue gas cooler (13) is used to replace part of the low-pressure heater (10), thereby achieving energy-saving effects. Other systems are similar to the implementation case four.

The invention realizes cascaded utilization of hot primary air, flue gas and slag waste heat, and heats cold source working fluids with appropriate temperature according to the temperature levels of the three waste heat resources of hot primary air, flue gas and slag, such as: high-temperature wind, low-temperature Wind, high-temperature water, and low-temperature water; considering the three waste heat resources of hot primary air, flue gas and slag, the thermal system is optimized and the economy of the thermal system is improved.

The invention utilizes bypass flue high-pressure economizer, bypass flue low-pressure economizer and hot primary air cooler equipment to heat the condensed water or feed water of the steam turbine regenerating system to replace part of the function of high or low heating. On the premise that the amount of coal burned remains unchanged, the power generation and the economy of the unit are improved.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (10)

1. A utility boiler multiple heterogeneous waste heat utilization system is characterized in that, according to the flow direction of the flue gas, it includes an air preheater, a dust collector, an induced draft fan and a flue gas cooler connected in series in sequence; There is also a flue gas bypass between the flue gas inlet and the flue gas outlet, and the flue gas bypass is connected in series with a bypass high-pressure economizer and a bypass low-pressure economizer; According to the direction of air circulation, the inlet of the air preheater is also fed with primary cold air and secondary cold air. The primary cold air passes through the air preheater and the hot primary air cooler in turn, and then merges with another primary air cooling channel and then enters the pulverized coal. Part of the secondary cold air is preheated by the air preheater and sent directly to the furnace, and the other part is sent to the furnace through the hot air slag cooler; According to the discharge direction of the slag, the system also includes a hot air slag cooler and a low temperature water cooled slag cooler connected in series. The secondary cold air is sent to the furnace; the water side of the low-temperature water-cooled slag trap is connected in parallel with the bypass low-pressure economizer. 2. A utility boiler multiple heterogeneous waste heat utilization system according to claim 1, characterized in that the air preheater is connected to the primary fan through a primary air heater, and the primary air heater is used for heating The primary cold air sent by the primary fan; the air preheater is connected with the blower through the secondary air heater, and the secondary air heater is used to heat the secondary cold air sent by the blower. 3. A utility boiler multiple heterogeneous waste heat utilization system as claimed in claim 2, characterized in that the flue gas cooler is connected to the primary air heater and the secondary air heater respectively through a closed circulating water system. connected. 4. A multi-component heterogeneous waste heat utilization system for utility boilers as claimed in claim 3, characterized in that the bypass high-pressure economizer and bypass low-pressure economizer are respectively connected in parallel with the high-pressure heater and the low-pressure heater. 5. A utility boiler multiple heterogeneous waste heat utilization system, characterized in that, according to the flow direction of the flue gas, it includes an air preheater, a dust collector, an induced draft fan and a flue gas cooler connected in series in sequence; There is also a flue gas bypass between the flue gas inlet and the flue gas outlet, and the flue gas bypass is connected in series with a bypass high-pressure economizer and a bypass low-pressure economizer; According to the direction of air circulation, the inlet of the air preheater is also fed with primary cold air and secondary cold air. The primary cold air passes through the air preheater and the hot primary air cooler in turn, and then merges with another primary air cooling channel and then enters the pulverized coal. Part of the secondary cold air is preheated by the air preheater and sent directly to the furnace, and the other part flows through the hot air slag cooler and then sent to the furnace; According to the slag discharge direction, the system also includes a low-temperature water-cooled slag device and a high-temperature water-cooled slag device connected in series. The high-temperature water-cooled slag device is directly installed at the bottom of the furnace. The road low-pressure economizers are connected in parallel. 6. A utility boiler multiple heterogeneous waste heat utilization system as claimed in claim 5, wherein the air preheater is connected to the primary fan through a primary air heater, and the primary air heater is used for heating The primary cold air sent by the primary fan; the air preheater is connected with the blower through the secondary air heater, and the secondary air heater is used to heat the secondary cold air sent by the blower. 7. A utility boiler multiple heterogeneous waste heat utilization system as claimed in claim 6, characterized in that the flue gas cooler is connected to the primary air heater and the secondary air heater respectively through a closed circulating water system. Connected; 8 . The multi-element and heterogeneous waste heat utilization system for utility boilers according to claim 7 , wherein the bypass high-pressure economizer and bypass low-pressure economizer are respectively connected to a high-pressure heater and a low-pressure heater. 9. A utility boiler multiple heterogeneous waste heat utilization system, characterized in that, according to the flow direction of flue gas, it includes an air preheater, a dust collector, an induced draft fan and a flue gas cooler connected in series in sequence; There is also a flue gas bypass between the flue gas inlet and the flue gas outlet, and the flue gas bypass is connected in series with a bypass high-pressure economizer and a bypass low-pressure economizer; According to the direction of air circulation, the inlet of the air preheater is also fed with primary cold air and secondary cold air. The primary cold air passes through the air preheater and the hot primary air cooler in turn, and then merges with another primary air cooling channel and then enters the pulverized coal. machine; the secondary cold air is sent to the furnace after being preheated by the air preheater; According to the direction of slag discharge, the system also includes a series connection of hot air slag cooler and low temperature air slag cooler, the hot air slag cooler is directly installed at the bottom of the furnace; the heated secondary cold air is sent to the air through the low temperature air slag cooler. Preheater. 10. A multi-element and heterogeneous waste heat utilization system for utility boilers according to claim 9, wherein the air preheater is directly connected to the primary fan, and the primary fan directly sends the primary cold air to the air preheater; The low-temperature air-cooled slag device is directly connected with the blower, and the blower sends the secondary cold air directly to the low-temperature air-cooled slag device.