CN103375792A - Engine-boiler coupled deep waste heat utilization system for air cooling unit - Google Patents

Abstract

The invention belongs to the field of energy saving and emission reduction of thermal power units, and in particular relates to a deep utilization system of residual heat coupled with a machine furnace of an air-cooling unit. The system mainly includes air preheater, multi-stage extraction air heater, feed water heater, condensate heater, low-temperature economizer; the first-stage extraction air heater uses exhaust steam to preheat air; other extraction Steam-type air heaters refer to steam extraction from low-level to high-level steam turbines to preheat air; the preheated air absorbs less heat in the air preheater, and the amount of flue gas required by the air preheater will also decrease, and the excess smoke will The gas leads to the bypass flue connected in parallel with the air preheater; a feed water heater and a condensate water heater are arranged in the bypass flue to heat the feed water and condensate water respectively, and squeeze out heat and extract steam to increase the work of the steam turbine. The system recycles and utilizes the exhaust steam of higher parameters of the air-cooling unit and the waste heat of low-level extraction steam, which improves the grade of heat and has a good energy-saving effect.

Description

Deep Utilization System of Waste Heat Coupling with Air Cooling Unit and Furnace

technical field

The invention belongs to the field of energy saving and emission reduction of thermal power units, and in particular relates to a deep utilization system of residual heat coupled with an air-cooling unit and a furnace.

Background technique

In order to reduce pollutant emissions and improve energy utilization efficiency, more and more large-capacity thermal power units have been put into use. But for water-poor and water-scarce areas, the water consumption of power plants has become a big problem with the simultaneous increase of unit capacity. At present, the main method to solve this problem is to use the air cooling system. Compared with wet cooling, the outstanding advantage of air cooling is water saving. This system uses the air in the environment to condense the exhaust steam of the steam turbine, which can reduce the water supply of the power plant by 75%. However, due to the high back pressure of air-cooled units and low thermal cycle efficiency, the coal consumption for power generation is higher than that of wet-cooled units, which is contrary to the original intention of investing in large-capacity thermal power units.

Contents of the invention

The present invention proposes a deep utilization system of residual heat coupled with an air-cooling unit, machine and furnace, which can reasonably recycle and utilize the heat of exhaust steam and low-level extraction steam of the steam turbine, so that the residual heat can be effectively utilized in an optimal form.

The technical scheme adopted in the present invention is:

In the boiler flue of this system, economizer, air preheater, feed water heater, and condensate heater are arranged in sequence. The exhaust steam of the steam turbine enters the hot well of the condenser, and then passes through the condensate pump, 7# heater, and 6# heating in sequence. The heater, 5# heater, deaerator, 3# heater, 2# heater, 1# heater are connected to the economizer,

Three-stage series extraction air heaters are arranged in front of the air preheater. The first-stage extraction air heater uses exhaust steam at the outlet of the steam turbine to heat the air, and the second-stage extraction air heater and the third-stage extraction The type air heater uses the 7th stage extraction steam and the 6th stage extraction steam to heat the air respectively. The preheated air is further heated in the air preheater and leads to the boiler furnace; the flue gas at the outlet of the economizer is divided into two One part flows through the air preheater, the temperature is lowered to heat the air, the other part enters the bypass flue and flows through the feed water heater and condensate water heater in turn, and the two parts of flue gas are combined and then lead to the dust removal and desulfurization system; The water side of the feed water heater is connected in parallel with 1# heater, 2# heater and 3# heater. The feed water enters the feed water heater from the inlet of the 3# heater through the regulating valve 18 for heating, and then returns to the outlet of the 1# heater. The condensed water heater is connected in parallel with the 5# heater, and the condensed water enters the condensed water heater from the inlet of the 5# heater through the regulating valve 19 for heating, and then returns to the outlet of the 5# heater.

The first-stage extraction air heater heats the air by recovering the heat of exhaust steam at the outlet of the steam turbine, and the exhaust steam releases heat to saturated water and then returns to the condenser hot well.

Cancel the first-stage steam extraction air heater, and set the air duct inlet of the second-stage steam extraction air heater above the air-cooled island, and the air with a higher temperature above the air-cooled island directly leads to the second-stage steam extraction air heater. Air heater for heating.

For units with relatively high exhaust gas temperature, a low-temperature economizer is installed at the end of the boiler flue, the outlet of the 7# heater is connected to the inlet of the low-temperature economizer, and the outlet of the low-temperature economizer is connected to the outlet of the 5# heater Ingress connection.

The beneficial effects of the present invention are:

The system extracts the exhaust steam to heat the air, recovers the heat of the exhaust steam of the air-cooling unit, and introduces part of the heat of the low-level extraction steam, thereby saving part of the heat of the high-temperature flue gas used for preheating the air. Installing feed water heat exchanger and condensate water heat exchanger in the bypass flue can recover the waste heat of these high-grade flue gas and use it to heat feed water and condensate water with higher parameters. The unit worked. The system realizes the recovery and utilization of the high-parameter exhaust steam and low-level extraction steam heat of the air-cooling unit. Based on the principle of energy matching and cascade utilization, the waste heat of the entire machine furnace can be optimally utilized, and the economic benefits are remarkable.

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the first implementation case of an air-cooling unit applying the present invention;

Fig. 2 is a schematic diagram of the system structure of the second embodiment of the air-cooling unit applying the present invention.

Labels in the figure:

1- Air preheater; 2- Feed water heater; 3- Condensate water heater; 4- Low temperature economizer; 5- Third stage extraction air heater; 6- Second stage extraction air heater ;7-first stage extraction air heater;8-1# heater;9-2# heater;10-3# heater;11-deaerator;12-5# heater;13-6 # heater; 14-7# heater; 15-; 16- condenser hot well; 17- economizer; 18- regulating valve; 19- regulating valve; 20- regulating valve; 21- air cooling island.

Detailed ways

The invention proposes a waste heat deep utilization system coupled with an air-cooling unit and a furnace. The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

In the system structure schematic diagram of the first embodiment shown in Figure 1, the economizer 17, air preheater 1, feed water heater 2, and condensate water heater 3 are arranged in sequence in the boiler flue of the system; exhaust steam from the steam turbine enters the condensate Heater well 16, and then through condensate pump 15, 7# heater 14, 6# heater 13, 5# heater 12, deaerator 11, 3# heater 10, 2# heater 9, 1# heating After the device 8, it is passed into the economizer 17. The principle is: a three-stage extraction air heater is arranged in front of the air preheater 1, and the first-stage extraction air heater 7 uses the exhaust steam at the outlet of the steam turbine to heat the air, and the exhaust steam releases heat until the saturated water returns to the condensing steam Then the air enters the second-stage extraction air heater 6, and the second-stage extraction air heater 6 refers to the seventh-stage extraction to heat the air, and the seventh-stage extraction releases heat until the saturated water returns to 7 #The drain of the heater 14; then the air enters the third-stage extraction air heater 5, and the third-stage extraction air heater 5 uses the sixth-stage extraction to heat the air, and the sixth-stage extraction releases heat to saturation The water returns to the drain water of the 6# heater 13; the heated air is further heated in the air preheater 1 and then leads to the boiler furnace; the flue gas from the outlet of the economizer 17 is divided into two parts, and one part is preheated by air 1, the temperature is lowered to heat the air, and the other part enters the bypass flue and flows through the feed water heater 2 and the condensate heater 3 in sequence. Desulfurization system: the water side of the feed water heater 2 is connected in parallel with the 1# heater 8, the 2# heater 9 and the 3# heater 10, and the feed water enters the feed water heater 2 from the inlet of the 3# heater 10 through the regulating valve 18 for heating. Then return to the outlet of 1# heater 8; the condensed water heater 3 is connected in parallel with 5# heater 12, and the condensed water enters the condensed water heater 3 from the inlet of 5# heater 12 through the regulating valve 19 to be heated, and then returns to To the outlet of 5# heater 12.

A low-temperature economizer 4 is installed at the end of the boiler flue, the outlet of the 7# heater 14 is connected to the inlet of the low-temperature economizer 4, the outlet of the low-temperature economizer 4 is connected to the inlet of the 5# heater 12, and the feed water is supplied from 7# The inlet of the heater 14 enters the condensate heater 3 for heating through the regulating valve 20, and then returns to the inlet of the 5# heater 12.

Fig. 2 is a schematic diagram of the system structure of the second implementation case. The difference of this implementation case is that the first-stage extraction air heater 7 with exhaust steam as the heat source is omitted, and the second-stage extraction air heater The air of 6 directly leads from above air cooling island 21. Since the inlet air in this embodiment comes from above the air-cooling island 21, the inlet air temperature is relatively high, which is close to the design inlet temperature of the second-stage extraction air heater 6, so basically the same energy-saving effect as that in the first embodiment can be obtained .

Claims (4)

1. the waste heat deep exploitation system of Air-cooled Unit machine stove coupling, arrange successively economizer (17) in its boiler flue, air preheater (1), feed-water heater (2), condensation water heater (3), exhaust steam in steam turbine enters condenser hotwell (16), again successively by condensate pump (15), 7# heater (14), 6# heater (13), 5# heater (12), oxygen-eliminating device (11), 3# heater (10), 2# heater (9), pass into economizer (17) behind the 1# heater (8), it is characterized in that

Bled steam type air heater in three grades of series connection of the front layout of air preheater (1), first order bled steam type air heater (7) is quoted steam turbine outlet exhaust steam and is added hot-air, second level bled steam type air heater (6) and third level bled steam type air heater (5) quote respectively the 7th grade draw gas and the 6th grade draw gas and add hot-air, the air that is preheated is further heated and leads to boiler furnace at air preheater (1); The flue gas of economizer (17) outlet is divided into two parts, the part air preheater (1) of flowing through, temperature reduces for adding hot-air, another part enters bypass flue and flow through successively feed-water heater (2) and condensation water heater (3), leads to dedusting and desulphurization system after two parts flue gas converges; The water side of feed-water heater (2) is in parallel with 1# heater (8), 2# heater (9) and 3# heater (10), feedwater enters feed-water heater (2) heating from 3# heater (10) porch through control valve 18, returns the exit of 1# heater (8); Condensation water heater (3) is then in parallel with 5# heater (12), and condensate water enters condensation water heater (3) heating from 5# heater (12) porch through control valve 19, returns the exit of 5# heater (12).

2. the waste heat deep exploitation system of a kind of Air-cooled Unit machine stove coupling according to claim 1, it is characterized in that: described first order bled steam type air heater (7) adds hot-air by reclaiming steam turbine outlet exhaust steam heat, and the exhaust steam heat release turns back to condenser hotwell (16) to saturation water.

3. the waste heat deep exploitation system of a kind of Air-cooled Unit machine stove coupling according to claim 1, it is characterized in that: cancel described first order bled steam type air heater (7), the air channel entrance of second level bled steam type air heater (6) is arranged at Air-Cooling Island (21) top, and the air that Air-Cooling Island (21) top temperature is higher directly leads to second level bled steam type air heater (6) and heats.

4. the waste heat deep exploitation system of a kind of Air-cooled Unit machine stove coupling according to claim 1, it is characterized in that: for the relatively high unit of exhaust gas temperature, the end of described boiler flue arranges low-level (stack-gas) economizer (4), the outlet of 7# heater (14) is connected with the entrance of low-level (stack-gas) economizer (4), and the outlet of low-level (stack-gas) economizer (4) is connected with the entrance of 5# heater (12).

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