CN2755450Y - System for preventing boiler air preheater from low temperature corrosion - Google Patents

Abstract

The utility model discloses a system for avoiding low-temperature corrosion of a boiler air preheater. The system includes: an air preheater (1), an air channel (9) for providing air distribution to the boiler, boiler feed water, air The preheater (1) is arranged in the air duct (9), and boiler feed water enters the air preheater (1) as a working medium for heating the boiler and distributing air. It can fundamentally prevent low-temperature corrosion and ash blocking on the heating surface of the air preheater, and avoid boiler efficiency reduction caused by low-temperature corrosion and ash blocking in the air preheater. It can reduce the operating cost, repair and maintenance of the air preheater, and play a role in saving the production cost of the power plant.

Description

A System for Avoiding Low Temperature Corrosion of Boiler Air Preheater

technical field

The utility model relates to a system which effectively utilizes the waste heat in the flue gas of a power plant boiler and can avoid low-temperature corrosion of the air preheater of the boiler, and is especially applied to a power plant boiler utilizing biomass to generate electricity. Among them, the biomass is crop straw, sawdust, branches and so on.

Background technique

The air preheater of the boiler in the prior art is mostly arranged in the flue of the boiler. CN2573978Y discloses an adjustable air supply device for heat exchange in the flue of the heating furnace. The heat exchange section of the flue of the heating furnace is connected with the air preheater, and the air induction pipe at the outlet of the air preheater is connected to the induced draft fan. The inlet is connected to the burner blown into the heating furnace through the outlet pipe of the induced draft fan. A regulating duct is added at the entrance of the induced draft fan. When the flue gas temperature at the outlet of the air preheater is lower than the dew point temperature of the flue gas, the air regulating pipe can be properly opened, thereby reducing the amount of air sucked by the air preheater, so as to keep the exhaust gas temperature constant at its dew point above temperature. US2002069836A1 discloses a device, which is applied to a boiler combustion gas preheating device. The preheating device is arranged in the flue, and is used to transfer the available heat in the flue gas to the combustion air entering the boiler combustion gas, thereby Realize energy saving.

The above two existing technologies all set the air preheater in the boiler flue. The inside of the air preheater uses air as the heating medium. When the high-temperature flue gas in the flue flows through the air preheater, the high-temperature flue gas The heat in the boiler is transferred to the internal heating medium cold air through the interface of the air preheater, so that the temperature of the cold air rises, and the heated hot air enters the burner of the boiler, thereby saving fuel. At the same time, since the cold air in the air preheater takes away the heat of the hot flue gas in the flue, the temperature of the hot flue gas can also be reduced. Thereby realizing the efficient utilization of energy.

Contents of the invention

In the prior art, the air preheater is installed in the flue, and flue gas and cold air are used to exchange heat. The heating surface on the flue gas side of the air preheater is prone to low-temperature corrosion and ash blocking. If the air preheater has low-temperature corrosion and clogging, it will cause heat transfer deterioration, reduce boiler efficiency, and increase boiler use and maintenance costs. And then lead to the increase of energy consumption of the draft fan and the draft fan.

In order to overcome the low-temperature corrosion on the flue gas side that is prone to occur on the heating surface of the air preheater of the power generation boiler in the prior art, a system for avoiding low-temperature corrosion of the boiler air preheater is provided, thereby increasing the service life of the air preheater and improving the transmission efficiency. Thermal efficiency, reduce boiler use and maintenance costs, reduce energy consumption, and fundamentally prevent low-temperature corrosion and ash blocking on the heating surface of the air preheater.

The technical solution adopted by the utility model to solve the technical problem is: a system for avoiding low-temperature corrosion of the boiler air preheater, which is characterized in that the system includes: an air preheater 1 for providing air distribution to the boiler The air duct 9, the deaerator or feed water tank for providing boiler feed water and the flue, the air preheater 1 is arranged in the air duct 9, and the deaerator or feed water tank is connected with the air preheater 1.

The system also includes a flue gas cooler 2 arranged in the flue, and the air preheater 1 is connected with the flue gas cooler 2 .

The system also includes an economizer 3 arranged in the flue, and the air preheater 1 is connected to the economizer 3 .

The system also includes an economizer 3 arranged in the flue, and the flue gas cooler 2 is connected with the economizer 3 .

The system also includes a flue gas cooler 2 and an economizer 3 arranged in the flue, the air preheater 1 is connected with the flue gas cooler 2 and the economizer 3 respectively, and the flue gas cooler 2 is connected with the economizer 3 connections.

The interior of the air preheater 1 is a tube bundle composed of finned tubes and or bare tubes.

The inside of the flue gas cooler 2 is a tube bundle composed of finned tubes and or bare tubes.

The boiler is a boiler that utilizes biomass to generate electricity, and the biomass is crop straw, sawdust or tree branches.

An air preheater is arranged in the air duct at the outlet of the blower. The inside of the air preheater is a tube bundle composed of finned tubes, bare tubes or other structural forms of the heating surface. The heated working medium outside the heating surface is air; The working medium is hot water, which comes from boiler feed water. After the air passes through the air preheater, it absorbs part of the heat from the boiler feed water. The heated hot air is directly used as boiler combustion air distribution, namely - boiler ignition air, main fuel air in the lower part of the boiler and boiler secondary air.

Since the air preheaters are all arranged in the air duct and do not use flue gas-air heat exchange, there is no problem of low-temperature corrosion and ash blocking. An air preheater is arranged in the air duct at the outlet of the blower. The air preheater uses boiler feed water as the heating medium. After the boiler feed water enters the air preheater, part of the heat in the boiler feed water is transferred to the air side, and the heating comes from the ambient temperature. The heated air is directly used as the boiler combustion air distribution, namely - the boiler ignition air, the main fuel air in the lower part of the boiler and the boiler secondary air. Because the air preheater does not use flue gas as the heating medium, it can fundamentally prevent low temperature corrosion of the air preheater.

In order to ensure the efficiency of the boiler, the boiler must have a relatively low exhaust heat loss, and the exhaust gas temperature must be reduced to a certain limit, so there must be sufficient heating surfaces for cooling in the flue. Therefore, in addition to the superheater and economizer, a flue gas cooler is also arranged in the flue. Proper control of water temperature and boiler exhaust gas temperature can make the wall temperature of the cold end of the flue gas cooler higher than the flue gas dew point temperature, preventing low-temperature corrosion. Moreover, various forms of soot blowers can be used to remove the ash accumulation on the heat transfer surface of the flue gas cooler, so as to prevent the ash accumulation from corroding the wall surface and improve the heat transfer efficiency.

The function of the feed water control valve is to adjust the flow of boiler feed water entering the flue gas cooler, adjust the heat absorption, water temperature and exhaust gas temperature of the flue gas cooler according to different fuels and boiler loads, and ensure that the boiler has good efficiency. At the same time, it can prevent the temperature of the wall surface of the flue gas cooler from being lower than the dew point temperature of the flue gas, thereby preventing low-temperature corrosion.

The beneficial effects of the utility model are: (1) fundamentally prevent low-temperature corrosion and ash blocking on the heating surface of the air preheater, and avoid boiler efficiency reduction caused by low-temperature corrosion and ash blocking in the air preheater. (2) It can reduce the operating cost, repair and maintenance of the air preheater, and play a role in saving the production cost of the power plant.

Description of drawings:

Below in conjunction with accompanying drawing and embodiment the utility model is described further.

Accompanying drawing 1 is the schematic flow chart of the preferred embodiment of the present utility model.

In Figure 1: 1. Air preheater, 2. Flue gas cooler, 3. Economizer, 4. Deaerator or feed water tank, 5. Feed water control valve, 6. Fan, 7. Boiler feed water pump, 8 , Boiler air distribution 9, air duct, 10, flue, 11, bypass.

Detailed ways

In Fig. 1, a system for avoiding low-temperature corrosion of the boiler air preheater, an air preheater 1 is arranged in the air duct 9 supplying air to the boiler burner, and the inside of the air preheater is composed of finned tubes and bare tubes The heated working medium in the air preheater 1 is air; the heated working medium is hot water, and the hot water can come from the deaerator, the boiler feed water tank, or is available hot water from other parts. After the air in the air duct 9 passes through the air preheater, it absorbs part of the heat in the hot water, and the heated hot air is directly used as boiler air distribution, and the water cooled by the air preheater 1 leaves the air preheater 1 Finally, it enters the water supply control valve 5, and is divided into two paths by the water supply control valve 5 outlet. All the way into the flue gas cooler 2, the flue gas cooler 2 is a tube bundle composed of finned tubes, light tubes or other structural forms of the heating surface, set in the boiler flue 10, the water medium in the flue gas cooler 2 and the flow The hot flue gas passing through the flue 10 performs heat exchange, absorbs the heat in the hot flue gas, and then flows out of the flue gas cooler 2 . The hot water flowing out of the flue gas cooler 2 enters the economizer 3 arranged in the flue 10 , and then flows out of the economizer 3 . The other path directly passes through the bypass 11, merges with the hot water medium flowing out of the flue gas cooler 2, then enters the economizer 3, and then flows out of the economizer 3. Of course, all the outlet water from the air preheater 1 can also enter the flue gas cooler 2, and then enter the economizer. Or all the outlet water from the air preheater 1 directly enters the economizer flue gas cooler 2 .

In a preferred embodiment of the system for avoiding low temperature corrosion of boiler air preheater, it includes air preheater 1, flue gas cooler 2, economizer 3, deaerator or feed water tank 4, feed water control Valve 5, fan 6, boiler feed water pump 7, boiler air distribution 8, air duct 9, flue 10. The inside of the air preheater 1 is a tube bundle composed of finned tubes, bare tubes or other structural heating surfaces, which are arranged in the air duct 9, and the fan 6 is used to supply the boiler air distribution 8 to the air duct 9, and the economizer 3 and the flue gas cooler 2 are sequentially arranged in the flue 10 according to the direction of flue gas flow, and the flue gas cooler is a tube bundle composed of finned tubes and light tubes or a heating surface in other structural forms. The deaerator or feed water tank provides hot water to the air preheater 1 through the boiler feed water pump 7, as the working fluid for heating the air in the air passage 9 in the air preheater 1, and the heated air is used as the boiler air distribution 8. The outlet water of the air preheater 1 is divided into two paths through the water supply control valve 5, one path is connected to the flue gas cooler 2, the outlet water of the flue gas cooler 2 is connected to the economizer 3, and the other path directly enters the economizer 3. Of course, all the outlet water from the air preheater 1 can also enter the flue gas cooler 2, and then enter the economizer. Or all the outlet water from the air preheater 1 directly enters the economizer flue gas cooler 2 .

The above embodiments are only preferred implementations of the system for avoiding low-temperature corrosion of boiler air preheaters claimed in the present utility model. Those skilled in the art can make further improvements and changes on this basis, but all fall within the protection scope of the utility model without departing from the essence of the utility model.

Claims (7)

1. A system for avoiding low-temperature corrosion of a boiler air preheater, characterized in that the system includes: an air preheater (1), an air duct (9) for providing air distribution to the boiler, and a duct for providing boiler feed water The deaerator or the water supply tank and the flue, the air preheater (1) is arranged in the air duct (9), and the deaerator or the water supply tank is connected with the air preheater (1). 2. The system for avoiding low-temperature corrosion of the boiler air preheater as claimed in claim 1, further comprising a flue gas cooler (2) arranged in the flue, the air preheater (1) and the flue gas cooler ( 2) connect. 3. The system for avoiding low-temperature corrosion of the air preheater according to claim 1, characterized in that: it also includes an economizer (3) arranged in the flue, the air preheater (1) and the economizer (3) Connection. 4. The system for avoiding low-temperature corrosion of the air preheater according to claim 2, characterized in that: it also includes an economizer (3) arranged in the flue, a flue gas cooler (2) and an economizer (3) Connection. 5. The system for avoiding low-temperature corrosion of the air preheater according to claim 1, characterized in that it also includes a flue gas cooler (2) and an economizer (3) arranged in the flue, and the air preheating The device (1) is respectively connected with the flue gas cooler (2) and the economizer (3), and the flue gas cooler (2) is connected with the economizer (3). 6. The system for preventing low-temperature corrosion of the air preheater according to any one of claims 1-5, characterized in that the interior of the air preheater (1) is a tube bundle composed of finned tubes and or bare tubes. 7. The system for preventing low-temperature corrosion of air preheaters according to any one of claims 2, 4 or 5, characterized in that the interior of the flue gas cooler (2) is a tube bundle composed of finned tubes and or bare tubes.

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