Flue gas waste heat utilization system for ultra-supercritical power station

Abstract

According to the flue gas waste heat utilization system for the ultra-supercritical power station, flue gas waste heat of a boiler is used for heating condensed water to replace part of regenerative self-use steam, and therefore the effects of energy conservation and emission reduction are achieved. The condenser, the condensate pump, the shaft seal cooler, the 8 # low-pressure heater, the 7 # low-pressure heater, the 6 # low-pressure heater, the 5 # low-pressure heater and the deaerator are sequentially connected through a condensate main pipeline; the water inlet section of the condensed water bypass pipeline is connected with the condensed water main pipeline, and the connection point is located between the 8 # low-pressure heater and the 7 # low-pressure heater; the water outlet section of the condensed water bypass pipeline is connected with the condensed water main pipeline, and the connection point is located between the 6 # low-pressure heater and the 5 # low-pressure heater; the condensed water bypass pipeline is connected with the water side of the flue gas heat exchanger; a flue gas heat exchanger flow regulating valve and a flow measuring device are arranged on the water inlet section of the condensed water bypass pipeline, and a temperature measuring point is arranged on the water outlet section of the condensed water bypass pipeline.

Description

Technical Field

[0001] The utility model relates to an ultra-supercritical power station flue gas waste heat utilization system. Background Art

[0002] Cycle thermal efficiency and boiler efficiency are the most important factors affecting the economic efficiency of coal-fired power plants, and boiler exhaust loss is the largest item of boiler heat loss, accounting for about 70% to 90% of boiler heat loss, and is the main factor affecting boiler efficiency.

[0003] Most power station boilers are equipped with economizers, air preheaters, waste heat recovery equipment and other equipment in the tail flue to recover the heat of exhaust gas and reduce the exhaust temperature. Coking in the boiler furnace and ash accumulation in the economizer and air preheater will reduce the heat transfer performance of the boiler heating surface and increase the exhaust temperature. Frequent changes in the type of coal and large deviations between the coal quality and the original design coal quality will cause the exhaust temperature to be much higher than the design value. In addition, the high sulfur content of the coal will increase the flue gas acid dew point and limit the operation of the tail equipment, so that the exhaust temperature cannot be reduced to the design value.

[0004] The exhaust gas temperature directly affects the thermal efficiency of the boiler. When the exhaust gas temperature is reduced by 10-15℃, the coal consumption for power generation can be reduced by 1 gram. It can be seen that the boiler exhaust gas contains a large amount of waste heat resources. If the unit operation can make full use of the flue gas waste heat, it can achieve the purpose of improving the overall operation efficiency, reducing the boiler coal consumption, saving energy, and reducing greenhouse gas emissions.

[0005] At present, more and more large-scale thermal power generating units are beginning to bear a large proportion of the heating load. The existing condensate water system of ultra-supercritical steam turbine generator units is as follows: Figure 1 As shown, the condensate is heated step by step by the low-pressure heater and then enters the deaerator. The low-pressure heaters at each stage can only be heated by the extraction steam from the steam turbine unit, which wastes the waste heat of the boiler flue gas. Utility Model Content

[0006] The purpose of the utility model is to overcome the above-mentioned deficiencies in the prior art and to provide a supercritical power plant flue gas waste heat utilization system with a reasonable structural design, which utilizes the flue gas waste heat of the boiler to heat condensate to replace part of the heat-recovered self-use steam, thereby achieving the effect of energy saving and emission reduction.

[0007] The technical solution adopted by the utility model to solve the above problems is: an ultra-supercritical power plant flue gas waste heat utilization system, including a deaerator, a 5# low-pressure heater, a 6# low-pressure heater, a 7# low-pressure heater, an 8# low-pressure heater, a shaft seal cooler, a condenser, a flue gas heat exchanger, a condensate pump and a condensate main pipeline; the condenser, the condensate pump, the shaft seal cooler, the 8# low-pressure heater, the 7# low-pressure heater, the 6# low-pressure heater, the 5# low-pressure heater, and the deaerator are connected in sequence through the condensate main pipeline; it is characterized in that: it also includes a flue gas heat exchanger The condensate bypass pipeline is connected to the flue gas heat exchanger flow regulating valve and the condensate bypass pipeline; the water inlet section of the condensate bypass pipeline is connected to the condensate main pipeline, and the connection point is located between the 8# low-pressure heater and the 7# low-pressure heater; the water outlet section of the condensate bypass pipeline is connected to the condensate main pipeline, and the connection point is located between the 6# low-pressure heater and the 5# low-pressure heater; the condensate bypass pipeline is connected to the water side of the flue gas heat exchanger; a flue gas heat exchanger flow regulating valve and a flow measuring device are arranged on the water inlet section of the condensate bypass pipeline, and a temperature measuring point is arranged on the water outlet section of the condensate bypass pipeline.

[0008] The utility model also comprises a dust collector and an induced draft fan, and the flue gas heat exchanger, the dust collector and the induced draft fan are connected in sequence.

[0009] The utility model is provided with a temperature measuring point at the inlet of the 5# low-pressure heater.

[0010] The utility model also includes a hot desalted water replenishment pipeline and a hot desalted water replenishment regulating valve. The hot desalted water replenishment pipeline is connected to the condensate main pipeline, and the connection point is located between the 8# low-pressure heater and the shaft seal cooler; the hot desalted water replenishment regulating valve is arranged on the hot desalted water replenishment pipeline.

[0011] Compared with the prior art, the utility model has the following advantages and effects: the waste heat of the boiler flue gas is used to heat the condensate to replace part of the heat-recovered steam for self-use, which effectively reduces the amount of low-pressure heating steam, that is, the amount of steam for self-use of the steam turbine generator set, reduces the flue gas temperature and recovers the waste heat of the boiler flue gas, improves the thermal efficiency of the entire unit, and can reduce the water consumption of the tail flue gas treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The schematic diagram of the structure of the condensate system of the existing ultra-supercritical steam turbine generator set in pure condensing operation is shown in FIG.

[0013] Figure 2 It is a structural schematic diagram of an embodiment of the utility model.

[0014] Figure 3 It is a logic flow chart of the working method of the embodiment of the utility model. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and through examples. The following examples are provided to explain the present invention, but the present invention is not limited to the following examples.

[0016] The embodiment of the utility model includes a deaerator 1, a 5# low-pressure heater 2, a 6# low-pressure heater 3, a 7# low-pressure heater 4, an 8# low-pressure heater 5, a shaft seal cooler 6, a condenser 7, a flue gas heat exchanger 8, a condensate pump 9, a hot desalted water make-up pipeline 10, a condensate bypass pipeline 11, a hot desalted water make-up regulating valve 12, a flue gas heat exchanger flow regulating valve 13, a dust collector 14, an induced draft fan 15 and a condensate main pipeline 16.

[0017] The condenser 7, condensate pump 9, shaft seal cooler 6, 8# low-pressure heater 5, 7# low-pressure heater 4, 6# low-pressure heater 3, 5# low-pressure heater 2, and deaerator 1 are connected in sequence through the condensate main pipeline 16. The condensate of the condenser 7 passes through the condensate pump 9, shaft seal cooler 6, 8# low-pressure heater 5, 7# low-pressure heater 4, 6# low-pressure heater 3, and 5# low-pressure heater 2 in sequence and then enters the deaerator 1.

[0018] The flue gas heat exchanger 8, the dust collector 14 and the induced draft fan 15 are connected in sequence, and the flue gas at the air preheater outlet passes through the flue gas heat exchanger 8, the dust collector 14 and the induced draft fan 15 in sequence and is then sent into the chimney.

[0019] The water inlet section of the condensate bypass pipeline 11 is connected to the condensate main pipeline 16, and the connection point is located between the 8# low-pressure heater 5 and the 7# low-pressure heater 4; the water outlet section of the condensate bypass pipeline 11 is connected to the condensate main pipeline 16, and the connection point is located between the 6# low-pressure heater 3 and the 5# low-pressure heater 2. The condensate bypass pipeline 11 is connected to the water side of the flue gas heat exchanger 8. After the condensate is drawn out from the 8# low-pressure heater 5, the condensate temperature is increased from about 75°C to about 100°C through the flue gas heat exchanger 8, and then sent to the inlet of the 5# low-pressure heater 2.

[0020] A flue gas heat exchanger flow regulating valve 13 and a flow measuring device are provided on the water inlet section of the condensate bypass pipeline 11, and a temperature measuring point is provided on the water outlet section of the condensate bypass pipeline 11. The opening of the flue gas heat exchanger flow regulating valve 13 is interlocked with the temperature measuring point signal provided on this line, and the opening of the flue gas heat exchanger flow regulating valve 13 is used to control the condensate flow through the condensate bypass pipeline 11, thereby ensuring that the condensate temperature at the outlet of the flue gas heat exchanger 8 is consistent with that of the condensate main pipeline 16. The adjustment process ensures that the flue gas temperature at the outlet of the flue gas heat exchanger 8 is controlled above the minimum allowable flue gas temperature. When the flue gas temperature at the outlet of the flue gas heat exchanger 8 is close to the minimum flue gas temperature limit, the main control logic is to ensure the flue gas temperature.

[0021] A temperature measuring point is set at the inlet of 5# low-pressure heater 2.

[0022] The hot desalted water replenishment pipeline 10 is connected to the condensate main pipeline 16, and the connection point is located between the 8# low-pressure heater 5 and the shaft seal cooler 6; a hot desalted water replenishment regulating valve 12 is provided on the hot desalted water replenishment pipeline 10. The newly prepared desalted water of the chemical water station is replenished into the condensate system through the hot desalted water replenishment pipeline 10 and the hot desalted water replenishment regulating valve 12 after heat exchange with the heating condensate return water, so that the heating condensate return water of qualified quality is recovered. The opening of the hot desalted water replenishment regulating valve 12 is interlocked with the deaerator liquid level. When the ultra-supercritical unit is in heating condition, the deaerator liquid level is controlled by this valve group.

[0023] like Figure 3 As shown, the working method of the embodiment of the utility model is:

[0024] (1) According to the actual operating conditions, set the operating temperature, pressure parameters and target liquid level of deaerator 1.

[0025] (2) When the ultra-supercritical unit is operating normally under heating conditions, the actual liquid level is judged whether it is within the preset control target liquid level range through the liquid level measurement point signal set on the deaerator 1. When the actual liquid level is higher than the control target liquid level range, the opening of the hot desalted water feed regulating valve 12 is interlocked to decrease, otherwise the opening is interlocked to increase. By dynamically adjusting the opening of the hot desalted water feed regulating valve 12, the liquid level of the deaerator 1 is maintained normal and stable.

[0026] (3) The working temperature of the condensate at the outlet of the condensate main line 16 and the bypass flue gas heat exchanger 8 is measured by the temperature measuring points T1 and T2 set on the condensate system pipeline. When the condensate system measuring point T2 < T1, that is, the condensate temperature at the outlet of the flue gas heat exchanger 8 is lower than the condensate temperature at the outlet of the 6# low-pressure heater 3, the opening of the flue gas heat exchanger flow control valve 13 is interlocked to decrease, otherwise the opening is interlocked to increase. By dynamically adjusting the opening of the flue gas heat exchanger flow control valve 13, the water temperature of the condensate bypass pipeline 11 is maintained consistent with that of the main line 16.

[0027] (4) After the water temperature of the condensate bypass pipeline 11 is consistent with that of the condensate main pipeline 16, determine again whether the working liquid level of the deaerator 1 is normal. If not, return to the second step and adjust the opening of the hot desalted water make-up regulating valve 12 to adjust the liquid level of the deaerator 1 until the liquid level of the deaerator 1 and the water temperatures of the condensate main pipeline 16 and the condensate bypass pipeline 11 meet the control requirements.

[0028] (5) By using the liquid level measurement point signal set on the condenser 7 equipment, it is determined whether the actual liquid level is within the control target liquid level range. When the actual liquid level is higher than the control target liquid level range, the interlock control condensate pump 9 flow rate increases, otherwise the interlock control condensate pump 9 flow rate decreases. By dynamically adjusting the flow rate of the condensate pump 9, the liquid level of the condenser 7 is maintained normal and stable.

[0029] (6) After the condenser 7 liquid level is adjusted normally, determine again whether the deaerator 1 working liquid level is within the target range. If not, adjust the opening of the hot desalted water make-up regulating valve 12 to adjust the deaerator 1 liquid level. Through repeated adjustments, the deaerator 1 liquid level, condenser 7 liquid level, and the condensate main pipeline 16 and condensate bypass pipeline 11 temperatures can dynamically meet the requirements.

[0030] After the implementation of this utility model, it is estimated that about 22,000 tons of standard coal can be saved each year, carbon dioxide emissions can be reduced by 55,000 tons, sulfur dioxide emissions can be reduced by 528 tons, and nitrogen oxide emissions can be reduced by 154 tons. The initial calculation of the investment recovery period is 4 years, and there is also the income of carbon emission rights. After implementation, the economic efficiency of the unit has been significantly improved.

[0031] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different, and the above content described in this specification is only an example of the structure of the utility model. All equivalent changes or simple changes made based on the structure, features and principles described in the patent concept of the utility model are included in the protection scope of the utility model patent. Technicians in the technical field of the utility model can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the utility model or exceed the scope defined by the claims, they should all fall within the protection scope of the utility model.

Claims

1. An ultra-supercritical power plant flue gas waste heat utilization system, comprising a deaerator, a 5# low-pressure heater, a 6# low-pressure heater, a 7# low-pressure heater, an 8# low-pressure heater, a shaft seal cooler, a condenser, a flue gas heat exchanger, a condensate pump and a condensate main pipeline; the condenser, the condensate pump, the shaft seal cooler, the 8# low-pressure heater, the 7# low-pressure heater, the 6# low-pressure heater, the 5# low-pressure heater and the deaerator are connected in sequence through the condensate main pipeline; characterized in that: It also includes a flue gas heat exchanger flow regulating valve and a condensate bypass pipeline; the water inlet section of the condensate bypass pipeline is connected to the condensate main pipeline, and the connection point is located between the 8# low-pressure heater and the 7# low-pressure heater; the water outlet section of the condensate bypass pipeline is connected to the condensate main pipeline, and the connection point is located between the 6# low-pressure heater and the 5# low-pressure heater; the condensate bypass pipeline is connected to the water side of the flue gas heat exchanger; a flue gas heat exchanger flow regulating valve and a flow measuring device are arranged on the water inlet section of the condensate bypass pipeline, and a temperature measuring point is arranged on the water outlet section of the condensate bypass pipeline.

2. The ultra-supercritical power plant flue gas waste heat utilization system according to claim 1 is characterized in that: It also includes a dust collector and an induced draft fan, and the flue gas heat exchanger, the dust collector and the induced draft fan are connected in sequence.

3. The ultra-supercritical power plant flue gas waste heat utilization system according to claim 1 is characterized in that: A temperature measuring point is set at the inlet of the 5# low-pressure heater.

4. The ultra-supercritical power plant flue gas waste heat utilization system according to claim 1 is characterized in that: It also includes a hot desalted water make-up pipeline and a hot desalted water make-up regulating valve. The hot desalted water make-up pipeline is connected to the condensate water main pipeline, and the connection point is located between the 8# low-pressure heater and the shaft seal cooler; a hot desalted water make-up regulating valve is arranged on the hot desalted water make-up pipeline.

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