CN204730177U - Residual heat from boiler fume cascade utilization device - Google Patents

Abstract

The utility model relates to a boiler flue gas waste heat cascade utilization device, which comprises a flue gas system, an air system and a closed circulating water system. The flue gas system includes a first heat exchanger, an air preheater, a second heat exchanger, a dust collector, a third heat exchanger and a desulfurization device connected in sequence, the first heat exchanger is connected in parallel with the air preheater, The air system includes a pre-air preheater and an air preheater connected in sequence, and the closed circulating water system includes a closed circulating water pump, the water outlet of the closed circulating water pump, the third heat exchanger, the second heat exchanger, the front The water inlet of the air preheater and the closed circulation water pump are connected in sequence to form a water closed circulation loop. The utility model recovers the waste heat of the flue gas through the first heat exchanger, the second heat exchanger and the third heat exchanger, which not only completes the three-stage utilization of the waste heat of the flue gas, improves the energy conversion efficiency of the coal-fired unit, but also It is beneficial to reduce the dust emission concentration of the dust collector and the water consumption of the desulfurization device, and improve production efficiency.

Description

Boiler flue gas waste heat cascade utilization device

technical field

The utility model relates to the technical field of boiler waste heat recovery, in particular to a boiler flue gas waste heat cascade utilization device.

Background technique

With the development of the economy, the society's demand for electricity continues to increase. More than 70% of power plants are coal-fired power plants. At present, the energy utilization rate of coal-fired power plants is low, and most of the waste heat energy is discharged into the environment. In the heat loss of boilers, the heat loss of power plant exhaust smoke accounts for a large proportion. In the actual operation of the boiler, due to the influence of factors such as dust on the heating surface, the exhaust gas temperature of the boiler is often higher than the design temperature, which will not only reduce the boiler efficiency and increase the coal consumption rate; but also increase the dust emission concentration of the dust collector. It will cause environmental pollution; and it will also increase the amount of water sprayed during wet desulfurization, resulting in a large waste of water resources.

Utility model content

The purpose of the utility model is to provide a boiler flue gas waste heat cascade utilization device, which can reduce the flue gas discharge temperature, realize the utilization of flue gas waste heat, and improve the energy conversion efficiency of the coal-fired unit.

For realizing the purpose of this utility model, the technical scheme that takes is:

A boiler flue gas waste heat cascade utilization device, including a flue gas system, an air system, and a closed circulating water system. The flue gas system includes a first heat exchanger, an air preheater, a second heat exchanger, and a dust removal heat exchanger, third heat exchanger and desulfurization device, the first heat exchanger is connected in parallel with the air preheater, the air system includes the front air preheater and air preheater connected in sequence, and the closed water circulation system includes closed circulation Water pump, third heat exchanger, second heat exchanger and front air preheater, water outlet of closed circulation water pump, third heat exchanger, second heat exchanger, front air preheater and closed The water inlets of the circulating water pump are connected in sequence to form a closed water circulation loop.

The high-temperature flue gas from the boiler enters the first heat exchanger and the air preheater, and after the first heat exchanger and the air preheater perform heat exchange and cooling on the high-temperature flue gas, the low-temperature flue gas enters the second heat exchanger, and the second The heat exchanger performs heat exchange and cooling of the flue gas in one step through the closed water circulation loop, and then the flue gas enters the dust collector for dust removal, and the flue gas after dust removal enters the third heat exchanger, and the third heat exchanger further cools the flue gas through the water circulation loop. After heat exchange and cooling, the flue gas enters the desulfurization device for desulfurization, and the desulfurized flue gas is discharged into the atmosphere; the air required for boiler combustion first enters the front air preheater and preheats through the closed water circulation circuit, and then Then enter the air preheater, under the action of high-temperature flue gas, the air is further heated, and finally enters the boiler for combustion; the water medium of the closed water circulation loop passes through the third heat exchanger and the second heat exchanger, and then is heated by the flue gas Heating, the heated water medium heats the normal temperature air entering the pre-air preheater, so that the waste heat of the flue gas can be used reasonably. Preheat the air entering the air preheater and increase the air temperature at the air inlet end of the air preheater. On the premise of ensuring that the temperature of the air discharged from the air preheater meets the combustion requirements of the boiler, the heat of the flue gas from the air preheater The demand is reduced, and when the high-temperature flue gas at the inlet of the air preheater is constant, the excess flue gas heat enters the first heat exchanger to complete the first-stage utilization of the flue gas waste heat; the flue gas also passes through the second heat exchanger After the heat exchanger enters the dust collector, the temperature of the flue gas at the inlet of the dust collector is actively controlled, which is beneficial to reduce the concentration of dust emissions, and the water medium in the closed water circulation loop is heated by the flue gas entering the second heat exchanger , to complete the second-level utilization of flue gas waste heat; finally, the flue gas enters the desulfurization device after passing through the third heat exchanger, actively controls the flue gas temperature at the inlet of the desulfurization device, reduces the water consumption of the desulfurization device, and uses the third heat exchanger The flue gas of the heater heats the water medium of the closed water circulation loop to complete the third-level utilization of the waste heat of the flue gas, which greatly improves the energy conversion efficiency of the coal-fired unit.

The technical scheme is further described below:

Further, the boiler flue gas waste heat cascade utilization device also includes an economizer and a deaerator, the first heat exchanger includes a high-temperature smoke-water heat exchanger and a low-temperature smoke-water heat exchanger, and the water side of the high-temperature smoke-water heat exchanger The water outlet is connected to the water inlet of the economizer, and the water side outlet of the low-temperature smoke-water heat exchanger is connected to the water inlet of the deaerator. The feed water is heated through the high-temperature smoke-water heat exchanger, and the condensed water is heated through the low-temperature smoke-water heat exchanger to improve the energy conversion efficiency of the unit and increase production efficiency.

Further, the boiler flue gas waste heat cascade utilization device also includes a feedwater regulating valve and a high-pressure heater, and the feedwater regulating valve and the high-pressure heater are connected in parallel to the water side of the high-temperature flue-water heat exchanger after being connected in series. The amount of feed water entering the high-temperature flue-water heat exchanger is controlled by the feed-water regulating valve, so that the temperature of the feed water at the outlet of the high-temperature flue-water heat exchanger is higher than the temperature of the feed water at the outlet of the high-pressure heater, and the temperature of the feed water entering the economizer is increased to make the boiler smoke The structural design of the gas waste heat cascade utilization device is more reasonable.

Further, the boiler flue gas waste heat cascade utilization device also includes a condensate regulating valve and a low-pressure heater, and the condensate regulating valve and the low-pressure heater are connected in parallel to the water side of the low-temperature smoke-water heat exchanger after being connected in series. The amount of condensed water entering the low-temperature smoke-water heat exchanger is controlled by the condensate regulating valve, so that the temperature of the condensed water at the outlet of the low-temperature smoke-water heat exchanger is higher than the temperature of the condensed water at the outlet of the low-pressure heater, increasing the temperature of the condensed water entering the deaerator , so that the structural design of the boiler flue gas waste heat cascade utilization device is more reasonable.

Further, the flue gas system further includes a first flue gas regulating valve, and the first flue gas regulating valve is connected between the first heat exchanger and the boiler. The heat of the flue gas entering the first heat exchanger is adjusted through the first flue gas regulating valve, that is, the heat of the flue gas entering the air preheater is adjusted at the same time, so that the air temperature at the outlet of the air preheater meets the combustion requirements of the boiler, and the adjustment is simple and flexible .

Further, the flue gas system further includes a second flue gas regulating valve, and the second flue gas regulating valve is connected in parallel with the third heat exchanger. The flue gas temperature at the flue gas inlet of the desulfurization device is adjusted through the second flue gas regulating valve and the third heat exchanger.

Further, the flue gas system also includes an induced draft fan, the inlet of the induced draft fan is connected with the outlet of the dust collector, and the outlet of the induced draft fan is respectively connected with the second flue gas regulating valve and the third heat exchanger. The induced draft fan pressurizes the incoming flue gas, and transports the flue gas to the desulfurization device for desulfurization.

Further, an expansion tank is also connected to the closed water circulation circuit. The expansion tank buffers the volume expansion caused by the heating of water in the closed water circulation circuit.

Further, the closed circulation water pump is a frequency conversion water pump. The frequency conversion water pump controls the water flow in the closed water circulation loop, and adjusts the flue gas temperature at the outlet of the second heat exchanger and the third heat exchanger.

Further, the air system also includes a blower, one end of the blower is an air inlet, and the other end is connected to the pre-air preheater. The air is delivered to the front air preheater by the blower.

Compared with the prior art, the utility model has the following beneficial effects:

The utility model increases the air temperature at the air inlet end of the air preheater by preheating the air entering the air preheater, and on the premise that the air temperature at the outlet of the air preheater meets the combustion requirements of the boiler, the air preheater The heat demand of the flue gas is reduced, and under the condition that the high-temperature flue gas at the inlet of the air preheater is constant, the excess flue gas heat enters the first heat exchanger to complete the first-stage utilization of the flue gas waste heat; also makes the flue gas The gas enters the dust collector after passing through the second heat exchanger, actively controlling the temperature of the flue gas at the inlet of the dust collector, which is beneficial to reduce the concentration of dust emissions, and uses the flue gas entering the second heat exchanger to heat the air to complete Second-level utilization of flue gas waste heat; finally, the flue gas enters the desulfurization device after passing through the third heat exchanger, actively controls the temperature of the flue gas at the inlet of the desulfurization device, reduces the water consumption of the desulfurization device, and uses the third heat exchanger The flue gas heats the air, completes the third-level utilization of the waste heat of the flue gas, and improves the energy conversion efficiency of the coal-fired unit.

Description of drawings

Fig. 1 is a structural schematic diagram of a boiler flue gas waste heat cascade utilization device according to an embodiment of the utility model.

Explanation of reference signs:

10. Closed circulating water pump, 210. First heat exchanger, 211. High-temperature smoke-water heat exchanger, 212. Low-temperature smoke-water heat exchanger, 220. Second heat exchanger, 230. Dust collector, 240. Third Heat exchanger, 250. Desulfurization device, 260. First flue gas regulating valve, 270. Second flue gas regulating valve, 280. Induced fan, 310. Front air preheater, 320. Blower fan, 50. Air preheating 610. Feedwater regulating valve, 620. High pressure heater, 630. Economizer water inlet, 640. Feedwater pump, 710. Condensate regulating valve, 720. Low pressure heater, 730. Deaerator, 80. Expansion water tank.

Detailed ways

Embodiment of the utility model is described in detail below in conjunction with accompanying drawing:

As shown in Figure 1, a boiler flue gas waste heat cascade utilization device includes a flue gas system, an air system and a closed circulating water system. The heat exchanger 50, the second heat exchanger 220, the dust remover 230, the third heat exchanger 240 and the desulfurization device 250, the first heat exchanger 210 and the air preheater 50 are connected in parallel, and the air system includes pre- Air preheater 310, air preheater 50 and boiler 40, closed circulating water system includes closed circulating water pump 10, third heat exchanger 240, second heat exchanger 220 and front air preheater 310, closed The water outlet of the type circulating water pump 10, the third heat exchanger 240, the second heat exchanger 220, the pre-air preheater 310 and the water inlet of the closed circulating water pump 10 are sequentially connected to form a closed water circulation loop.

The high-temperature flue gas from the boiler 40 enters the first heat exchanger 210 and the air preheater 50. After the first heat exchanger 210 and the air preheater 50 perform heat exchange and cooling on the high-temperature flue gas, the flue gas enters the second heat exchanger The second heat exchanger 220 and the second heat exchanger 220 further exchange heat and cool down the flue gas through a closed water circulation loop, and then the flue gas enters the dust collector 230 for dust removal, and the dust-removed flue gas enters the third heat exchanger 240, and the third heat exchanger The device 240 further performs heat exchange and cooling of the flue gas through a closed water circulation loop, and then the flue gas enters the desulfurization device 250 for desulfurization, and the flue gas is discharged into the atmosphere after desulfurization; the air required for the combustion of the boiler 40 first enters the front air for preheating The air preheater 310 is preheated, and then enters the air preheater 50. Under the action of high-temperature flue gas, the air is further heated, and finally enters the boiler 40 for combustion; the water medium of the closed water circulation loop passes through the third heat exchanger 240 And the second heat exchanger 220 is heated by the flue gas, and the heated water medium heats the normal temperature air entering the pre-air preheater 310, so that the waste heat of the flue gas can be reasonably used. The air entering the air preheater 50 is preheated, and the air temperature at the air inlet of the air preheater 50 is increased. Then, on the premise that the air temperature at the outlet of the air preheater 50 meets the combustion requirements of the boiler 40, the air preheater The heat demand of the flue gas at 50 is reduced, and when the high-temperature flue gas at the inlet of the air preheater 50 is constant, the excess flue gas heat enters the first heat exchanger 210 to complete the first-stage utilization of the waste heat of the flue gas; Also make the flue gas pass through the second heat exchanger 220 and then enter the dust collector 230, actively control the temperature of the flue gas at the inlet of the dust collector 230, which is beneficial to the concentration of dust emissions, and use the flue gas entering the second heat exchanger 220 The air is heated to complete the second-level utilization of the waste heat of the flue gas; finally, the flue gas passes through the third heat exchanger 240 and then goes to the desulfurization device 250, actively controls the temperature of the flue gas at the inlet of the desulfurization device 250, and reduces the temperature of the desulfurization device 250 The water consumption is reduced, and the flue gas from the third heat exchanger 240 is used to heat the air to complete the third-level utilization of the waste heat of the flue gas, which greatly improves the energy conversion efficiency of the coal-fired unit.

In this embodiment, as shown in FIG. 1 , the air system further includes a blower 320 , one end of the blower 320 is an air inlet, and the other end is connected to the pre-air preheater 310 . The air is delivered to the pre-air preheater 310 by the blower 320 . And the second heat exchanger 220 and the third heat exchanger 240 are both low-temperature smoke-water heat exchangers.

As shown in Figure 1, the flue gas system also includes a first flue gas regulating valve 260, which is connected between the first heat exchanger 210 and the boiler 40, and the first flue gas regulating valve 260 is connected to the first flue gas regulating valve 260. The heat exchanger 210 is arranged in parallel with the air preheater 50 after being connected in series. The heat of the flue gas entering the first heat exchanger 210 is adjusted through the first flue gas regulating valve 260, that is, the heat of the flue gas entering the air preheater 50 is adjusted at the same time, so that the air temperature at the outlet of the air preheater 50 meets the temperature of the boiler 40. Combustion requirements, adjustment is simple and flexible.

As shown in FIG. 1 , the first heat exchanger 210 includes a high-temperature smoke-water heat exchanger 211 . The water side outlet of the high-temperature smoke-water heat exchanger 211 is connected to the water inlet 630 of the economizer, and the feedwater regulating valve 610 and the high-pressure heater 620 are arranged in parallel with the high-temperature smoke-water heat exchanger 211. The high-temperature smoke-water heat exchanger The water side water inlet of 211 is also connected with the outlet main pipe of the feed water pump 640 . The feed water is heated through the high-temperature smoke-water heat exchanger 211, and the amount of feed water entering the high-temperature smoke-water heat exchanger 211 is controlled by the feed water regulating valve 610, so that the temperature of the feed water at the outlet of the high-temperature smoke-water heat exchanger 211 is higher than that of the high-pressure heater The temperature of the feed water at the outlet of 620 increases the temperature of the feed water entering the economizer, so that the structural design of the boiler flue gas waste heat cascade utilization device is more reasonable.

As shown in Figure 1, the first heat exchanger 210 also includes a low-temperature smoke-water heat exchanger 212, the flue gas outlet of the high-temperature smoke-water heat exchanger 211 is connected to the flue gas inlet of the low-temperature smoke-water heat exchanger, and the boiler flue gas waste heat The cascade utilization device also includes a condensate regulating valve 710 and a low-pressure heater 720, the water side outlet of the low-temperature smoke-water heat exchanger 212 is connected to the water inlet of the deaerator 730, the condensate regulating valve 710 and the last stage of low-pressure heater 720 is arranged in parallel with the low-temperature smoke-water heat exchanger 212 after being connected in series. The condensed water entering the deaerator 730 is heated by the low-temperature smoke-water heat exchanger 212, and the amount of condensed water entering the low-temperature smoke-water heat exchanger 212 is controlled by the condensate regulating valve 710, so that the low-temperature smoke-water heat exchanger 212 The outlet condensed water temperature is higher than the condensed water temperature of the low-pressure heater 720, and the temperature of the condensed water entering the deaerator 730 is increased, so that the structural design of the boiler flue gas waste heat cascade utilization device is more reasonable.

As shown in FIG. 1 , the flue gas system further includes a second flue gas regulating valve 270 , and the second flue gas regulating valve 270 is arranged in parallel connection with the third heat exchanger 240 . The flue gas temperature at the inlet of the desulfurization device 250 is adjusted through the second flue gas regulating valve 270 and the third heat exchanger 240 .

As shown in Figure 1, the flue gas system also includes an induced draft fan 280, the inlet of the induced draft fan 280 is connected to the outlet of the dust collector 230, and the outlet of the induced draft fan 280 is connected to the second flue gas regulating valve 270 and the third heat exchanger 240 respectively . The induced draft fan 280 pressurizes the incoming flue gas, and transports the flue gas to the desulfurization device 250 for desulfurization.

As shown in FIG. 1 , an expansion tank 80 is also connected to the closed water circulation circuit. The expansion water tank 80 buffers the volume expansion caused by the heating of water in the closed water circulation circuit.

In this embodiment, the closed circulation water pump 10 is a frequency conversion water pump. The variable frequency water pump controls the water flow in the closed water circulation loop, and adjusts the flue gas temperature at the outlets of the second heat exchanger 220 and the third heat exchanger 240 . The closed circulation water pump 10 can also be set as other forms of water pumps according to actual needs.

The utility model lowers the flue gas temperature to a suitable temperature by connecting multiple heating surfaces in parallel and in series at the tail of the boiler, wherein the high-temperature flue gas heat obtained from the primary utilization of flue gas waste heat passes through the high-temperature flue-water heat exchanger 211 to heat the feed water , the medium-temperature flue gas heat obtained from the secondary utilization of flue gas waste heat passes through the low-temperature flue-water heat exchanger 212 to heat the condensed water, and the low-temperature flue gas heat obtained from the tertiary utilization of flue gas waste heat passes through the second heat exchanger 220 and the third heat exchanger 240 to heat the air to complete the tertiary utilization of the waste heat of the flue gas and improve the energy conversion efficiency of the coal-fired unit.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the utility model, and the description thereof is relatively specific and detailed, but it should not be understood as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the scope of protection of the utility model patent should be based on the appended claims.

Claims (10)

1. A boiler flue gas waste heat cascade utilization device, characterized in that it includes a flue gas system, an air system and a closed circulating water system, and the flue gas system includes a first heat exchanger and an air preheater connected in sequence , a second heat exchanger, a dust remover, a third heat exchanger and a desulfurization device, the first heat exchanger is connected in parallel with the air preheater, and the air system includes pre-air preheaters connected in sequence and the air preheater, the closed circulating water system includes a closed circulating water pump, the third heat exchanger, the second heat exchanger and the front air preheater, the closed The water outlet of the circulating water pump, the third heat exchanger, the second heat exchanger, the pre-air preheater and the water inlet of the closed circulating water pump are sequentially connected to form a closed water circulation loop. 2. The boiler flue gas waste heat cascade utilization device according to claim 1, characterized in that it also includes an economizer and a deaerator, and the first heat exchanger includes a high-temperature smoke-water heat exchanger and a low-temperature smoke-water exchanger Heater, the water side outlet of the high-temperature smoke-water heat exchanger is connected to the water inlet of the economizer, and the water-side water outlet of the low-temperature smoke-water heat exchanger is connected to the water inlet of the deaerator . 3. The boiler flue gas waste heat cascade utilization device according to claim 2, further comprising a feedwater regulating valve and a high-pressure heater, after the feedwater regulating valve and the high-pressure heater are connected in series, they are connected to the high-temperature flue gas The water side of the water heat exchanger is connected in parallel. 4. The boiler flue gas waste heat cascade utilization device according to claim 2, further comprising a condensate regulating valve and a low-pressure heater, after the condensate regulating valve and the low-pressure heater are connected in series, connected to the The water side of the low-temperature smoke-water heat exchanger is connected in parallel. 5. The boiler flue gas waste heat cascade utilization device according to claim 1, characterized in that, the flue gas system further comprises a first flue gas regulating valve, and the first flue gas regulating valve is connected to the first exchanging valve between the heater and the boiler. 6. The boiler flue gas waste heat cascade utilization device according to claim 1, characterized in that the flue gas system further comprises a second flue gas regulating valve, and the second flue gas regulating valve is connected in parallel with the third heat exchanger connect. 7. The boiler flue gas waste heat cascade utilization device according to claim 6, wherein the flue gas system further comprises an induced draft fan, the inlet of the induced draft fan is connected to the outlet of the dust collector, and the induced draft fan The outlets of are respectively connected with the second flue gas regulating valve and the third heat exchanger. 8. The boiler flue gas waste heat cascade utilization device according to claim 1, characterized in that an expansion tank is also connected to the closed water circulation loop. 9. The boiler flue gas waste heat cascade utilization device according to claim 1, characterized in that the closed circulation water pump is a frequency conversion water pump. 10. The boiler flue gas waste heat cascade utilization device according to any one of claims 1 to 9, characterized in that the air system further includes a blower, one end of the blower is provided with an air inlet, and the other end is connected to the front Air inlet connection for air preheater.