System and method for utilizing waste heat of compression heat of high-pressure oxidation fan

Abstract

The invention provides a high-pressure oxidation fan compression heat waste heat utilization system and method which are integrated in a steam turbine power generation system and comprise a condensation water main pipeline and a multi-stage low-pressure heater connected to the main pipeline in series. The waste heat utilization heat exchanger is provided with a first channel and a second channel which are isolated from each other and exchange heat through a dividing wall; the first channel is connected to an outlet pipeline of the desulfurization oxidation fan in series; the water taking pipeline is connected between the condensed water main pipeline in front of the inlet of the last-stage low-pressure heater and the inlet of the second channel; the water return pipeline is connected between the outlet of the second channel and the water return position switching device; and the water return position switching device selectively returns the heated condensed water to the condensed water main pipeline at the outlet of the previous second-stage or previous first-stage low-pressure heater of the last-stage low-pressure heater. High-temperature oxidation air at the outlet of the oxidation fan is used for heating condensed water and returning the condensed water to the corresponding low-pressure heater, so that steam extraction of a heat regeneration system and the water amount of a desulfurization system are reduced, and energy conservation and consumption reduction are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal power generation, and further relates to a high-pressure oxidation fan compression heat waste heat utilization system and method. BACKGROUND

[0002] In a desulfurization system (especially the main limestone-gypsum wet desulfurization), the oxidation fan is a core auxiliary equipment for ensuring the desulfurization efficiency and realizing the resource recovery of gypsum, and its running state directly affects the stability and economy of the desulfurization system. Its core function is to introduce compressed air into the absorption slurry pool in the desulfurization tower, convert the intermediate product generated in the desulfurization process into recoverable gypsum through oxidation reaction, and maintain the normal working condition of the slurry in the tower. The specific functions include: 1. realizing calcium sulfite oxidation to generate gypsum; 2. oxidation air is sprayed from the gas distribution pipe / aeration device at the bottom of the absorption tower slurry pool, forming a large number of bubbles and moving upwards to produce strong stirring effect on the slurry, which can effectively prevent solid particles from depositing; 3. adjusting water quality, controlling slurry pH value, and stabilizing the desulfurization environment.

[0003] The working principle is: the oxidation fan inhales clean air from the environment, compresses the air according to the pressure requirement of the desulfurization system, converts the normal pressure air into high pressure air, and delivers the compressed high pressure air to the bottom of the absorption tower through the fan outlet pipeline, and disperses it into fine bubbles through the gas distribution device. The bubbles and the slurry are in full contact to complete the reaction.

[0004] In the process of converting normal pressure air into high pressure air by air compression, the oxidation fan converts the electrical energy consumed by the fan into internal energy of the air, and the temperature of the high pressure oxidation air rises. However, too high temperature of the high pressure oxidation air will have adverse effects on the desulfurization system, mainly including: (1) destroying the desulfurization reaction balance; The desulfurization reaction in the absorption tower (such as limestone-gypsum wet desulfurization) needs to be carried out at a relatively low temperature (usually 50-60°C), and high temperature oxidation air will break this balance.

[0005] decrease absorption efficiency: high temperature will reduce the solubility of the absorption slurry in the flue gas, resulting in unable to be effectively captured, and the concentration of the outlet flue gas exceeds the standard.

[0006] inhibit gypsum crystallization: oxidation air is the key to oxidizing calcium sulfite to calcium sulfate (gypsum), and too high temperature will interfere with the normal crystallization process of gypsum, which may generate fine white by-products (such as calcium sulfite) instead of qualified gypsum dihydrate.

[0007] (2) accelerate equipment wear and failure; ​High temperature oxidation air will cause direct damage to the internal components of the absorption tower and related equipment.

[0008] Corrosion aggravation: High temperature will accelerate the aging speed of the absorption tower lining (such as glass flake, rubber), and may change the pH stability of the slurry, leading to an increase in the corrosion rate of the tower wall and internal pipes (such as spray pipe, oxidation air pipe).

[0009] Excessive evaporation of slurry moisture: High temperature will cause rapid evaporation of moisture in the absorption slurry, leading to an increase in slurry concentration and viscosity, which may cause problems such as spray nozzle blockage and agitator overload.

[0010] (3) Chain reaction: triggering system chain failure; A single problem may spread to the entire desulfurization system instability.

[0011] Gypsum dehydration difficulty: If the generated gypsum is of poor quality (containing impurities or poor crystallization), the subsequent vacuum belt dehydrator will not be able to effectively dehydrate, leading to excessive water content in the gypsum, which cannot be normally discharged or reused.

[0012] Increased energy consumption and maintenance cost: To offset the impact of high temperature, the system may need to supplement additional cooling water or increase the amount of slurry circulation, directly increasing the operating energy consumption; at the same time, equipment corrosion and blockage will lead to a significant increase in maintenance frequency and cost.

[0013] Therefore, certain measures need to be taken to reduce the oxidation air temperature to a reasonable temperature before entering the desulfurization tower.

[0014] Currently, for the limestone-gypsum wet desulfurization process of thermal power generating units, the oxidation air temperature at the outlet of the high-pressure oxidation air blower can reach about 130℃, and the high-pressure oxidation air at 130℃ directly entering the desulfurization absorption tower will destroy the reaction environment in the absorption tower, leading to a decrease in desulfurization efficiency, inhibition of gypsum crystallization, and equipment damage. Therefore, under normal circumstances, a route of desuperheating water needs to be set for the high-temperature oxidation air pipeline, and the desuperheating water from the process water system reduces the oxidation air temperature to 50℃ to 60℃ before entering the desulfurization absorption tower. Although the traditional scheme reduces the oxidation air temperature to a suitable temperature for the reaction environment of the absorption tower, the waste heat of the oxidation air is not fully utilized, increasing the water consumption of the system. SUMMARY

[0015] The technical problem to be solved by the present application is to provide a high-pressure oxidation air blower compression heat waste heat utilization system and method. A condensate water bypass is provided in the condensate water main pipeline, the condensate water bypass is connected in series with the second channel of the waste heat utilization heat exchanger, the first channel is connected in series with the oxidation air blower, the heat is dissipated through the partition wall between the first channel and the second channel to reduce the oxidation air temperature, and at the same time, the waste heat is used for the regenerative system of the power plant, achieving the purpose of energy saving and consumption reduction.

[0016] The embodiment of the present application provides a high-pressure oxidation fan compression heat waste heat utilization system integrated in a steam turbine power generation system, comprising: a condensate main pipeline and a plurality of low-pressure heaters connected in series on the main pipeline, comprising: The waste heat utilization heat exchanger has a first channel and a second channel which are isolated from each other and exchange heat through a partition wall; the first channel is connected in series on an outlet pipeline of a desulfurization oxidation fan; The condensate bypass comprises: A water taking pipeline is connected between the condensate main pipeline before the inlet of the last-stage low-pressure heater and the inlet of the second channel; A backwater pipeline is connected between the outlet of the second channel and a backwater position switching device; The backwater position switching device selectively returns the heated condensate to the condensate main pipeline at the outlet of the second-stage low-pressure heater or the first-stage low-pressure heater before the last-stage low-pressure heater.

[0017] Optionally, the backwater position switching device comprises: A first backwater branch pipeline is connected between the outlet of the backwater pipeline and the condensate main pipeline at the outlet of the first-stage low-pressure heater; A second backwater branch pipeline is connected between the outlet of the backwater pipeline and the condensate main pipeline at the outlet of the second-stage low-pressure heater.

[0018] Optionally, the backwater position switching device further comprises on-off control valves arranged in the first backwater branch pipeline and the second backwater branch pipeline, respectively.

[0019] Optionally, a flow distribution device for adjusting flow is arranged on the water taking pipeline, and the flow distribution device distributes the condensate to the last-stage low-pressure heater and the condensate bypass.

[0020] Optionally, the flow distribution device adjusts the condensate flow into the condensate bypass to be not higher than 20% of the total flow of the condensate main pipeline at the water taking point.

[0021] Optionally, the flow distribution device comprises: a third electric shut-off valve, an electric regulating valve and a third manual shut-off valve arranged in series on the water taking pipeline, and a fourth manual shut-off valve connected in parallel with the third electric shut-off valve, the electric regulating valve and the third manual shut-off valve.

[0022] Optionally, the flow distribution device comprises: an adjustable three-way valve connected with the water taking pipeline inlet, the condensate main pipeline inlet of the last-stage low-pressure heater and the condensate outlet of the drain cooler, respectively.

[0023] Optionally, the multi-stage low-pressure heater comprises: a first low-pressure heater as the last-stage low-pressure heater, a second low-pressure heater as the first-stage low-pressure heater, and a third low-pressure heater as the second-stage low-pressure heater.

[0024] The embodiment of the present application also provides a high-pressure oxidation fan compression heat waste heat utilization method, which is used for the high-pressure oxidation fan compression heat waste heat utilization system and comprises: The outlet air temperature of the oxidation fan and the outlet water temperature of the waste heat utilization heat exchanger are monitored. According to a comparison result of the outlet air temperature of the oxidation fan and / or the outlet water temperature of the waste heat utilization heat exchanger and a corresponding preset threshold value, the action of the return water position switching device is controlled to select the return of the heated condensate water to the outlet of the second-stage low-pressure heater or the outlet of the first-stage low-pressure heater of the last-stage low-pressure heater.

[0025] Optionally, according to the comparison result of the outlet air temperature of the oxidation fan and / or the outlet water temperature of the waste heat utilization heat exchanger and the corresponding preset threshold value, the action of the return water position switching device is controlled to select the return of the heated condensate water to the outlet of the second-stage low-pressure heater or the outlet of the first-stage low-pressure heater of the last-stage low-pressure heater, and the method comprises the following steps. When the outlet air temperature of the oxidation fan is higher than or equal to a first air temperature threshold value and / or the outlet water temperature of the waste heat utilization heat exchanger is higher than or equal to a first water temperature threshold value, the return water switching device is controlled to return the condensate water to the outlet of the second-stage low-pressure heater. When the outlet air temperature of the oxidation fan is lower than the first air temperature threshold value and / or the outlet water temperature of the waste heat utilization heat exchanger is lower than the first water temperature threshold value, the return water switching device is controlled to return the condensate water to the outlet of the first-stage low-pressure heater.

[0026] The above scheme of the present application at least has the following beneficial effects. The above scheme of the present application provides a high-pressure oxidation fan outlet high-temperature oxidation wind waste heat utilization system, which utilizes the waste heat utilization heat exchanger with the first channel and the second channel which are isolated from each other and exchange heat through the partition wall, uses the waste heat of the oxidation fan to heat the condensate water, reduces the oxidation air temperature, uses the waste heat for the regenerative system of the power plant, reduces the steam extraction of the regenerative system, reduces the process water consumption of the desulfurization system, saves the water consumption of the desulfurization system, and realizes energy saving and consumption reduction. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Fig. 1 is a structural schematic diagram of a high-pressure oxidation fan compression heat waste heat utilization system provided by the present application; Figure 2is a structure diagram of fluid flow direction of a high-pressure oxidation fan compression heat waste heat utilization system provided by the application; Figure 3 is a flow diagram of a high-pressure oxidation fan compression heat waste heat utilization method provided by the application.

[0028] The reference signs are explained as follows: 1, air filter screen; 2, first butterfly valve; 3, oxidation fan; 4, corrugated compensator; 5, check valve; 6, second butterfly valve; 7, third butterfly valve; 8, flow measuring device; 9, waste heat utilization heat exchanger; 10, fourth butterfly valve; 11, air inlet pipeline; 12, air outlet main pipeline; 13, oxidation air branch pipeline; 14, water taking pipeline; 15, first stop valve; 16, second stop valve; 17, water return pipeline; 18, first manual stop valve; 19, first electric stop valve; 20, water return position switching device; 20a, second water return branch pipeline; 20b, first water return branch pipeline; 21, second manual stop valve; 22, second electric stop valve; 23, first condensate water main pipeline; 24, first electric gate valve; 25, second electric gate valve; 26, second condensate water main pipeline; 27, third electric gate valve; 28, fourth electric gate valve; 29, third electric stop valve; 30, electric regulating valve; 31, third manual stop valve; 32, fourth manual stop valve; 33, desulfurization absorption tower; 34, first low-pressure heater; 35, second low-pressure heater; 36, third low-pressure heater; 37, fourth low-pressure heater. DETAILED DESCRIPTION

[0029] Exemplary embodiments of the present application will be described herein below with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it is understood that the present application can be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0030] As shown in Figure 1 , an embodiment of the present application proposes a high-pressure oxidation fan compression heat waste heat utilization system integrated in a steam turbine power generation system, comprising: a condensate water main pipeline and multiple low-pressure heaters connected in series on the main pipeline, comprising: a waste heat utilization heat exchanger 9 having a first channel and a second channel isolated from each other and exchanging heat through an intermediate wall; wherein the first channel is connected in series on an outlet pipeline of a desulfurization oxidation fan 3; a condensate water bypass, the condensate water bypass comprising: a water taking pipeline 14 connected between the inlet of the second channel and the condensate water main pipeline before the inlet of the last-stage low-pressure heater; a backwater line 17 connected between the outlet of the second passage and the backwater position switching device 20; The backwater position switching device 20 selectively returns the heated condensate to the condensate main line at the outlet of the second-stage or first-stage low-pressure heater of the last-stage low-pressure heater.

[0031] The system of the embodiment of the present application is used in the regenerative system of a thermal power unit. The second passage of the waste heat utilization heat exchanger 9 is connected in series between the backwater line 17 and the water taking line 14, forming a part of the condensate bypass. The water inlet of the water taking line 14 is connected to the first condensate main line 23 before the inlet of the last-stage low-pressure heater. The condensate main line is connected to the outlet of the drain cooler. The condensate passing through the drain cooler flows to the last-stage low-pressure heater through the first condensate main line 23 and to the waste heat utilization heat exchanger 9 through the water taking line 14. The first passage of the waste heat utilization heat exchanger 9 is connected in series between the oxidizing air fan 3 and the desulfurization absorption tower 33. The high-temperature and high-pressure oxidizing air flowing out of the oxidizing air fan 3 passes through the first passage of the waste heat utilization heat exchanger 9, and heats the condensate in the second passage connected in parallel to the first passage and separated by a partition wall in a heat transfer manner, so as to reduce the temperature of the high-pressure oxidizing air to a preset temperature and enter the desulfurization absorption tower 33. At the same time, the heated condensate is returned to the corresponding low-pressure heater for recycling, thereby reducing the steam extraction amount of the low-pressure heater. The backwater position switching device 20 selectively returns the heated condensate to the corresponding low-pressure heater before the last-stage low-pressure heater according to the inlet / outlet air temperature of the oxidizing air fan and / or the condensate temperature in the backwater line 17. The inlet air temperature of the oxidizing air fan 3 affects the outlet air temperature thereof. According to the inlet / outlet air temperature of the oxidizing air fan 3, the condensate flow rate of the condensate bypass is adjusted in coordination, so as to control the high-temperature oxidizing air flowing through the first passage to be reduced to a preset temperature. According to the inlet / outlet air temperature of the oxidizing air fan 3 and / or the temperature of the heated condensate in the backwater line 17, the condensate is controlled to return to the condensate main line at the outlet of the second-stage or first-stage low-pressure heater before the last-stage low-pressure heater. When the inlet / outlet air temperature and / or the condensate temperature in the backwater line 17 is high, the condensate returns to the condensate main line at the outlet of the second-stage low-pressure heater. When the inlet / outlet air temperature and / or the condensate temperature in the backwater line 17 is low, the condensate returns to the condensate main line at the outlet of the first-stage low-pressure heater.

[0032] The embodiment of the present application realizes the synergistic energy saving at the whole plant level by integrating the waste heat of the desulfurization system into the regenerative system, and has significant economic value.

[0033] Taking newly built units as an example, newly built steam turbine generator units generally have a regenerative system with 9 or 10 stages of heat exchangers. Taking a regenerative system with 9 heat exchangers as an example, these are: High-pressure heater No. 1, High-pressure heater No. 2, High-pressure heater No. 3, Deaerator No. 4, Low-pressure heater No. 5, Low-pressure heater No. 6, Low-pressure heater No. 7, Low-pressure heater No. 8, and Low-pressure heater No. 9, with the No. 9 low-pressure heater being the final stage. Under different inlet air temperatures, the outlet air temperature of oxidation fan 3 will also vary. Reducing the high-temperature oxidation air to a preset temperature will also result in different amounts of heat released. The preset temperature is between 50℃ and 60℃, preferably 60℃. The condensate heating temperature varies depending on the inlet air temperature. In summer, the inlet air temperature of the oxidizer can reach 41.4℃, and the outlet air temperature of the oxidizer fan can reach 128℃. In spring and autumn, the inlet air temperature is only 20℃, and the outlet air temperature of the oxidizer fan is 100℃. After passing through the waste heat recovery heat exchanger, the temperature is reduced to 60℃. The heat released by the oxidizer air varies significantly with the season, which can, to some extent, regulate the condensate flow rate and control the cooling of the high-temperature oxidizer air to the preset temperature. However, the significant difference in heat release results in a substantial difference in the temperature of the heated condensate. To maximize the utilization of the heated condensate and achieve optimal energy saving, condensate at different temperatures needs to be switched back to the main condensate pipelines at the outlets of different low-pressure heaters to achieve optimal efficiency. Most directly, based on the condensate heating temperature, the return water switching device 20 can selectively return the heated condensate to the corresponding low-pressure heater, flexibly and fully utilizing the heated condensate, efficiently recovering waste heat, reducing the steam extraction volume of the corresponding low-pressure heater, and saving water consumption in the desulfurization system.

[0034] In an optional embodiment of the present invention, the waste heat utilization heat exchanger 9 is a shell-and-tube heat exchanger, wherein the first channel is the shell side for circulating oxidation air; and the second channel is the tube side for circulating condensate.

[0035] It should be noted that the first channel of the waste heat recovery heat exchanger 9 is the pipe connected in series in the shell side between the outlet pipe of the oxidation fan 3 of the desulfurization system and the inlet pipe of the desulfurization absorption tower 33; the second channel of the waste heat recovery heat exchanger is the pipe connected in series in the tube side between the water intake pipe 14 and the return water pipe 17. Both the first and second channels are internal pipes of the waste heat recovery heat exchanger and exchange heat through the partition wall.

[0036] like Figure 1 As shown, in an optional embodiment of the present invention, the flow direction of the high-temperature oxidizing air in the first channel within the waste heat utilization heat exchanger 9 is opposite to the flow direction of the low-temperature condensate in the second channel.

[0037] To achieve optimal heat exchange efficiency, the waste heat recovery heat exchanger 9 is preferably arranged in a counter-flow configuration. This counter-flow arrangement maintains a consistently high average temperature difference for heat exchange. The temperature is highest at the oxidation air inlet, where it encounters condensate that is about to flow out and has already risen in temperature; conversely, the temperature is lowest at the oxidation air outlet, where it encounters condensate that has just flowed in and has the lowest temperature. This results in a more uniform distribution of the driving force (temperature difference) for heat transfer across the entire heat exchange surface, thereby maximizing the recovery of the compression heat of the oxidation air and improving the overall thermal economy of the waste heat recovery system. Figure 1 The middle arrow indicates the direction of fluid flow.

[0038] In an optional embodiment of the present invention, the return water position switching device 20 includes: a first return water branch 20b connecting the outlet of the return water pipeline 17 and the outlet of the first-stage low-pressure heater; The second condensate main pipeline 26 and the second return water branch 20a are connected to the outlet of the return water pipeline 17 and the outlet of the first second-stage low-pressure heater.

[0039] In this embodiment, the inlet of the return water pipe 17 is connected to the outlet of the second channel, and the outlet of the return water pipe 17 is connected to the first return water branch 20b and the second return water branch 20a respectively, so as to return the heated condensate to the first stage low-pressure heater or the second stage low-pressure heater. It should be noted that the first return water branch 20b returns the heated condensate with a lower temperature to the main condensate pipe at the outlet of the first stage low-pressure heater, and the second return water branch 20a returns the heated condensate with a higher temperature to the main condensate pipe at the outlet of the second stage low-pressure heater.

[0040] In an optional embodiment of the present invention, the return water position switching device further includes: on / off control valves respectively disposed in the first return water branch 20b and the second return water branch 20a.

[0041] In this embodiment, the on / off control valve is used to control the on / off state of the first return water branch 20b or the second return water branch 20a. The control valve can be a set, consisting of a manual shut-off valve and an electric shut-off valve.

[0042] In another optional embodiment of the present invention, the return water position switching device 20 further includes a three-way stop valve connecting the first return water branch 20b, the second return water branch 20a and the return water pipeline 17.

[0043] In this embodiment, the three-way plug valve controls the opening and closing of the first return water branch 20b and the second return water branch 20a.

[0044] In an optional embodiment of the present invention, the main condensate pipeline selectively returning to the outlet of the second-stage or first-stage low-pressure heater preceding the final-stage low-pressure heater includes: Depending on different operating conditions, the on / off control valves on the first return water branch 20b and the second return water branch 20a are selectively controlled to open / close their states. When the valve of the first return water branch 20b is opened and the valve of the second return water branch 20a is closed, the heated condensate is returned to the main condensate pipeline at the outlet of the first-stage low-pressure heater. When the valve of the second return water branch 20a is opened and the valve of the first return water branch 20b is closed, the heated condensate is returned to the main condensate pipeline at the outlet of the second-stage low-pressure heater.

[0045] It should be noted that different operating conditions can refer to the temperature of the inlet / outlet air of the oxidation blower and / or the temperature of the condensate in the return water pipe 17. When the temperature of the inlet / outlet air of the oxidation blower and / or the temperature of the heated condensate reach the corresponding preset threshold, the control valve of the second return water branch 20a is opened, the control valve of the first return water branch 20b is closed, and the second return water branch is opened to return the higher temperature condensate to the main condensate pipe at the outlet of the second stage low-pressure heater. When the temperature of the inlet / outlet air of the oxidation blower and / or the temperature of the heated condensate do not reach the corresponding preset threshold, the control valve of the first return water branch 20b is opened, the control valve of the second return water branch 20a is closed, and the first return water branch is opened to return the lower temperature condensate to the main condensate pipe at the outlet of the first stage low-pressure heater.

[0046] In an optional embodiment of the present invention, a flow distribution device for regulating flow rate is provided on the water intake pipeline 14, and the flow distribution device distributes condensate to the final stage low-pressure heater and the condensate bypass.

[0047] In this embodiment, the inlet of the water intake pipe 14 can be directly connected to the condensate main pipe of the last-stage low-pressure heater to divert condensate. The water intake point of the water intake pipe 14 is located on the condensate main pipe between the outlet of the condensate cooler and the inlet of the last-stage low-pressure heater. Those skilled in the art can also adjust the water intake point according to the actual situation, which is not limited here.

[0048] In an optional embodiment of the present invention, the flow distribution device adjusts the flow rate of condensate flowing into the condensate bypass to be less than 20% of the total flow rate of the first condensate main pipeline 23 at the water intake point.

[0049] It should be noted that after being distributed by the flow distribution device, the flow rate of condensate flowing into the condensate bypass is no more than 20% of the total flow rate. In other words, most of the condensate enters the final stage low-pressure heater, and a small portion of the condensate enters the water intake pipe 14.

[0050] In an optional embodiment of the present invention, the flow distribution device includes: a regulating three-way valve, which is connected to the inlet of the water intake pipe 14, the inlet of the first condensate main pipe 23 of the last stage low-pressure heater, and the condensate outlet.

[0051] In this embodiment, by adjusting the regulating three-way valve, the condensate entering the main condensate pipe of the final stage low-pressure heater and the condensate entering the water intake pipe 14 are actively regulated, thereby achieving precise flow control. The regulating three-way valve can be installed on the pipe at the water intake point to regulate the flow rate of condensate to the final stage low-pressure heater and the water intake pipe 14.

[0052] In an optional embodiment of the present invention, the flow distribution device includes: a third electric shut-off valve 29, an electric regulating valve 30 and a third manual shut-off valve 31 connected in series in the water intake pipeline 14, and a fourth manual shut-off valve 32 connected in parallel with the third electric shut-off valve 29, the electric regulating valve 30 and the third manual shut-off valve 31.

[0053] In this embodiment, four valves are installed on the water intake pipe 14. By adjusting the water inlet flow of the condensate bypass, other water in the main pipe is directed to the condensate main pipe of the last stage low-pressure heater.

[0054] In an optional embodiment of the present invention, the multi-stage low-pressure heater includes: a first low-pressure heater 34 as the last stage low-pressure heater, a second low-pressure heater 35 as the preceding first stage low-pressure heater, and a third low-pressure heater 36 as the preceding second stage low-pressure heater.

[0055] In this embodiment, the condensate bypass draws water from the last stage, the first low-pressure heater. The condensate, heated by the waste heat exchanger 9, returns to the main condensate pipeline at the outlet of the second or third low-pressure heater. In another embodiment, the multi-stage low-pressure heater may include four or five stages. The condensate intake location can also be set according to actual conditions, and may be the second or third low-pressure heater. The heated condensate may also return to the first, second, or Nth stage low-pressure heater before the intake low-pressure heater, depending on the actual situation. As long as the principle is the same as that of this invention, it is within the protection scope of this invention.

[0056] like Figure 3 As shown, this embodiment of the invention also provides a method for utilizing the waste heat from the compression of a high-pressure oxidation blower, used in the aforementioned high-pressure oxidation blower waste heat utilization system, comprising: Step S10: Monitor the outlet air temperature of the oxidation fan 3 and the condensate outlet water temperature of the waste heat utilization heat exchanger 9.

[0057] Step S20: Based on the comparison results of the outlet air temperature of the oxidation blower 3 and / or the outlet water temperature of the waste heat utilization heat exchanger 9 and the corresponding preset threshold, control the operation of the return water position switching device to select to return the heated condensate to the outlet of the second-stage low-pressure heater or the first-stage low-pressure heater before the last-stage low-pressure heater.

[0058] In the method of this invention, the return water position switching device is controlled to operate according to the operating conditions. The operating conditions can be the inlet air temperature or the outlet air temperature of the oxidation blower. The inlet air temperature directly affects the outlet air temperature. The higher the inlet air temperature, the higher the temperature of the high-temperature and high-pressure air compressed by the oxidation blower. It needs to be cooled to a preset temperature before entering the desulfurization absorption tower. The more heat is released through the first channel of the waste heat utilization heat exchanger, the higher the temperature rise of the condensate in the second channel. Most directly, the condensate main pipeline returning to the first-stage low-pressure heater or the outlet of the first-stage low-pressure heater can be determined according to the temperature of the heated condensate and the corresponding preset threshold, so as to save maximum energy consumption.

[0059] In this embodiment of the invention, the preset threshold is the switching point with the highest cost-effectiveness determined after thermodynamic calculation. The preset threshold, compared with the outlet water temperature of the waste heat utilization heat exchanger 9, is set to a value close to the outlet water temperature of the first-stage low-pressure heater to ensure that the skip-stage operation can bring net energy-saving benefits. The integrated point (return water point) is dynamically adjusted according to the heat source quality (outlet water temperature) to achieve optimal energy matching and save maximum energy consumption.

[0060] In an optional embodiment of the present invention, the step of controlling the operation of the return water position switching device based on the comparison result of the outlet air temperature of the oxidation fan 3 and / or the outlet water temperature of the waste heat utilization heat exchanger 9 and a corresponding preset threshold, so as to select to return the heated condensate to the outlet of the second stage or the first stage low-pressure heater before the last stage low-pressure heater, includes: When the outlet air temperature of the oxidation blower 3 is higher than or equal to the first air temperature threshold, and / or the outlet water temperature of the waste heat utilization heat exchanger 9 is higher than or equal to the first water temperature threshold, the return water switching device is controlled to return the condensate to the main condensate pipeline of the outlet of the second-stage low-pressure heater. When the outlet air temperature of the oxidation blower 3 is lower than the first air temperature threshold, and / or the outlet water temperature of the waste heat utilization heat exchanger 9 is lower than the first water temperature threshold, the control return water switching device will return the condensate to the main condensate pipeline at the outlet of the first-stage low-pressure heater.

[0061] It should be noted that, depending on different operating conditions, selectively controlling the return of heated condensate to the corresponding low-pressure heater for optimal energy matching can maximize energy savings. When the outlet air temperature of the oxidation blower 3 is higher than or equal to the first air temperature threshold, and / or the outlet water temperature of the waste heat utilization heat exchanger 9 is higher than or equal to the first water temperature threshold, the return water switching device is controlled to return the condensate to the condensate main pipeline at the outlet of the second-stage low-pressure heater. In other words, the temperature of this condensate is already high enough that the second-stage, first-stage, and final-stage low-pressure heaters do not need to heat this condensate, saving the steam extraction volume of the three low-pressure heaters and achieving optimal energy saving. If this high-temperature condensate is returned to the outlet of the first-stage low-pressure heater, this high-temperature water enters the second-stage low-pressure heater and mixes with the water in the condensate main pipeline for cooling. The second-stage low-pressure heater still needs to extract steam to heat this cooled water. Although the steam extraction volume will be reduced, achieving a certain energy saving effect, it is not as optimal as the former, where steam extraction for this water is completely unnecessary. Energy saving not only considers the conservation of heat but also the conservation of energy or value. Higher temperature means higher value, and the condensate should be returned to the appropriate low-pressure heater to achieve even higher value and optimal energy savings. Different grades of low-pressure heaters have completely different specifications and energy levels. Higher-grade steam has greater work potential, but the cost of removing it is also higher. Therefore, for high-temperature condensate, returning it to the corresponding low-pressure heater is essential for achieving optimal energy savings.

[0062] When the outlet air temperature of the oxidation blower 3 is lower than the first air temperature threshold, and / or the outlet water temperature of the waste heat utilization heat exchanger 9 is lower than the first water temperature threshold, the return water switching device is controlled to return the condensate to the outlet of the first-stage low-pressure heater. Instead of returning this portion of the condensate to the second-stage low-pressure heater for steam extraction heating, which would consume more energy...

[0063] This embodiment has only two stages of low-pressure heaters with return flow, and the first water temperature threshold is close to the outlet water temperature of the first-stage low-pressure heater. In other embodiments, if there are multiple stages of low-pressure heaters with return flow, then multiple water temperature thresholds are set accordingly, each water temperature threshold being close to the outlet water temperature of the corresponding lower-stage low-pressure heater.

[0064] In an optional embodiment of the present invention, the operation of the return water position switching device is preferentially controlled based on the comparison result of the outlet water temperature of the waste heat utilization heat exchanger 9 and the corresponding preset threshold. When the water temperature monitoring fails, the operation of the return water position switching device is automatically switched to be controlled based on the comparison result of the outlet air temperature and the corresponding preset threshold. This reduces the steam extraction amount of the corresponding low-pressure heater and saves water consumption in the desulfurization system.

[0065] In this embodiment, using the outlet water temperature of the waste heat recovery heat exchanger 9 to control the return water position switching device is the most direct and accurate method.

[0066] Example 1: Currently, newly built steam turbine generator sets generally have 9 or 10 stages of heat exchangers. This example uses 9 heat exchangers, which are connected in series as follows: No. 1 high-pressure heater, No. 2 high-pressure heater, No. 3 high-pressure heater, No. 4 deaerator, No. 5 low-pressure heater, No. 6 low-pressure heater, No. 7 low-pressure heater, No. 8 low-pressure heater and No. 9 low-pressure heater, with No. 9 being the last stage low-pressure heater.

[0067] Taking two 1000MW units as an example, the inlet air volume of the oxidation blower is 43020m³. 3 The design operating condition is an inlet air temperature of 41.4℃ and an outlet air temperature of 128℃. To reduce the temperature of the oxidation air to 60℃ before it enters the desulfurization absorption tower, a desuperheating water volume of 2.52t / h is required.

[0068] When using the design condition of 41.4℃ inlet air temperature in this embodiment, the oxidation air temperature is reduced from 128℃ to 60℃, and the heat released by the oxidation air is 2122kW. This heat is used to heat the condensate at the inlet of low-pressure heater No. 9. The heated condensate is then returned to the outlet of low-pressure heater No. 7. Considering the heat exchange end difference of 10~15℃, the temperature of approximately 28t / h of condensate can be heated from 48.4℃ to 113℃. This reduces the steam extraction rate of low-pressure heaters No. 8 and No. 9 by 1t / h, reduces the steam extraction rate of low-pressure heater No. 7 by 1.26t / h, and saves 2.52t / h of desuperheating water.

[0069] When the inlet air temperature is 20℃, the outlet air temperature of the oxidation blower is 100℃. When it drops to 60℃, the oxidation air releases 1246kW of heat, which heats the condensate at the inlet of the No. 9 low-pressure heater. The heated condensate is then returned to the outlet of the No. 8 low-pressure heater. Considering the heat exchange end difference of 10~15℃, the temperature of approximately 27t / h of condensate can be heated from 48.4℃ to 85℃. This reduces the steam extraction rate of the No. 9 low-pressure heater by 0.96t / h and the steam extraction rate of the No. 8 low-pressure heater by 0.98t / h, saving 1.48t / h of desuperheating water.

[0070] In this embodiment of the high-pressure oxidation blower compression heat waste heat utilization system, when the inlet air temperature is high under design conditions, the condensate at the inlet of low-pressure heater No. 9 is heated, and the heated condensate is returned to the outlet of low-pressure heater No. 7. When the inlet air temperature is low, the condensate at the inlet of low-pressure heater No. 9 is heated, and the heated condensate is returned to the outlet of low-pressure heater No. 8.

[0071] like Figure 1As shown, the high-pressure oxidation blower compression heat recovery system of this embodiment includes: an oxidation blower inlet air filter 1; a first butterfly valve 2, i.e., an oxidation blower inlet butterfly valve; an oxidation blower 3; an oxidation blower outlet bellows compensator 4; an oxidation blower outlet check valve 5; a second butterfly valve 6, an oxidation blower outlet butterfly valve; a third butterfly valve 7, an oxidation blower outlet vent pipe butterfly valve; an oxidation blower outlet main pipe flow measurement device 8; a waste heat recovery heat exchanger 9; and a fourth butterfly valve 10, i.e., an oxidation blower branch butterfly valve; oxidation... 11. Fan inlet pipe; 12. Main outlet pipe of oxidation fan; 13. Oxidation fan branch pipe; 14. Water intake pipe, i.e., waste heat recovery condensate pipe; 15. First shut-off valve, shut-off valve for waste heat recovery condensate inlet pipe; 16. Second shut-off valve, i.e., shut-off valve for waste heat recovery condensate outlet pipe; 17. Return water pipe, i.e., waste heat recovery condensate outlet pipe; 18. First manual shut-off valve, i.e., manual shut-off valve for waste heat recovery condensate to outlet condensate of No. 7 low-pressure heater; 19. First electric shut-off valve, i.e., waste heat recovery condensate outlet condensate pipe. The system includes: an electric shut-off valve for the condensate outlet pipeline of low-pressure heater No. 7; a return water position switching device 20; a second return water branch 20a, i.e., the condensate outlet pipeline of low-pressure heater No. 7 for waste heat utilization; a first return water branch 20b, i.e., the condensate outlet pipeline of low-pressure heater No. 8 for waste heat utilization; a second manual shut-off valve 21, i.e., the manual shut-off valve for the condensate outlet pipeline of low-pressure heater No. 8 for waste heat utilization; and a second electric shut-off valve 22, i.e., the electric shut-off valve for the condensate outlet pipeline of low-pressure heater No. 8 for waste heat utilization. Electric shut-off valve; first electric gate valve 24 and second electric gate valve 25, namely the electric gate valve at the inlet of the condensate main pipeline 23 and the condensate main pipeline No. 7 low-pressure heater; second condensate main pipeline 26, namely the condensate pipeline at the outlet of the No. 7 low-pressure heater; third electric gate valve 27 and fourth electric gate valve 28, namely the electric gate valves at the outlet of the No. 7 low-pressure heater; third electric shut-off valve 29 on the water intake pipeline 14; electric regulating valve 30; third manual shut-off valve 31; fourth manual shut-off valve 32.

[0072] Three oxidation blowers 3 are connected in parallel. An air filter 1 and a first butterfly valve 2 are connected in series on the air inlet pipe 11 of each oxidation blower 3. A corrugated compensator 4, a check valve 5, a second butterfly valve 6 and a third butterfly valve 7 are connected in series on the outlet pipe of each oxidation blower 3. The outlet pipes of the three oxidation blowers 3 are connected to the outlet main pipe 12, which is equipped with a flow measurement device 8. The waste heat utilization heat exchanger 9 has a first channel and a second channel. The first channel is connected in series with the outlet main pipe 12. The outlet of the first channel is connected to the desulfurization absorption tower 33 through the oxidation air branch 13 of the main pipe.

[0073] Low-pressure heaters No. 7, No. 8, and No. 9 are connected in series via a condensate main pipeline. The condensate main pipeline of low-pressure heater No. 9 is connected to a condensate cooler. This invention includes a condensate bypass connecting to the inlet condensate main pipeline of low-pressure heater No. 9. The condensate bypass includes a water intake pipeline 14, which is equipped with a flow distribution device. The flow distribution device includes: a third electric shut-off valve 29, an electric regulating valve 30, a third manual shut-off valve 31, and a fourth manual shut-off valve 32 connected in series; and a fourth manual shut-off valve connected in parallel with the third electric shut-off valve 29, the electric regulating valve 30, the third manual shut-off valve 31, and the fourth manual shut-off valve 32. A second shut-off valve 16 and a first shut-off valve 15 are respectively installed on the return water pipeline 17 and the water intake pipeline 14 near the second channel of the waste heat utilization heat exchanger 9. The outlet of return water pipe 17 is connected to the first return water branch 20b and the second return water branch 20a. The first return water branch 20b is connected to the first condensate main pipe 23 at the outlet of low-pressure heater No. 8, and the second return water branch 20a is connected to the second condensate main pipe 26 at the outlet of low-pressure heater No. 7. The first return water branch 20b is connected in series with a second manual shut-off valve 21 and a second electric shut-off valve 22; the second return water branch 20a is connected in series with a first manual shut-off valve 18 and a first electric shut-off valve 19. The first condensate main pipe 23 at the outlet of low-pressure heater No. 8 is connected in series with a first electric gate valve 24 and a second electric gate valve 25, which are located on opposite sides of the first return water branch 20b. The second condensate main pipe 26 at the outlet of low-pressure heater No. 7 is equipped with a third electric gate valve 27 and a fourth electric gate valve 28, which are located on opposite sides of the second return water branch 20a.

[0074] The working process of a high-pressure oxidation blower compression heat waste heat utilization system in Example 1: Oxidation air system: Atmospheric pressure air is filtered through air filter 1 and then enters oxidation blower 3 through oxidation blower inlet butterfly valve 2. After being compressed by oxidation blower 3, it becomes high temperature and high pressure compressed air. After passing through oxidation blower outlet bellows compensator 4, oxidation blower outlet check valve 5, and oxidation blower outlet butterfly valve 6, it is combined and reaches oxidation blower outlet main pipe 12. After passing through flow measurement device 8, it enters waste heat utilization heat exchanger 9 and is reduced to the appropriate reaction temperature of desulfurization absorption tower. Then it is divided into multiple oxidation air branches 13 and enters desulfurization absorption tower. Oxidation air branch butterfly valves 10 are installed on oxidation air branches 13.

[0075] like Figure 2As shown, the condensate system is as follows: condensate from the condensate cooler flows to the first condensate main pipeline 23 and the waste heat utilization condensate intake pipeline 14 before the No. 9 low-pressure heater. Most of the condensate enters the first condensate main pipeline 23, and a small portion enters the waste heat utilization condensate intake pipeline 14. After passing through the first shut-off valve 15 of the waste heat utilization condensate inlet pipeline, it enters the waste heat utilization heat exchanger 9. After being heated by the waste heat utilization heat exchanger 9, it passes through the second shut-off valve 16 of the waste heat utilization condensate pipeline outlet and enters the waste heat utilization condensate outlet return pipeline 17. Under the design condition of an inlet air temperature of 41.4℃, the heated condensate returns to the second condensate main pipeline 26 at the outlet of the No. 7 low-pressure heater after passing through the first manual shut-off valve 18 and the first electric shut-off valve 19. Under the design condition of an inlet air temperature of 20℃, the heated condensate returns to the condensate pipeline at the outlet of the No. 8 low-pressure heater after passing through the second manual shut-off valve 21 and the second electric shut-off valve 22. A first electric gate valve 24 and a second electric gate valve 25 are installed on the inlet pipe of the No. 7 low-pressure heater, and a third electric gate valve 27 and a fourth electric gate valve 28 are installed on the outlet condensate pipe 26 of the No. 7 low-pressure heater.

[0076] The advantage of this embodiment is that it can effectively utilize the compression heat of the high-temperature oxidizing air at the outlet of the oxidizing blower, reduce the extraction of steam from the regenerating system, reduce the amount of process water used in the desulfurization system, save water consumption in the desulfurization system, and achieve the purpose of energy saving and consumption reduction.

[0077] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-pressure oxidizing blower compression heat waste heat utilization system, integrated into a steam turbine power generation system, comprising a condensate main pipeline and a multi-stage low-pressure heater connected in series on the main pipeline, characterized in that, include: A waste heat utilization heat exchanger (9) has a first channel and a second channel that are isolated from each other and exchange heat through a partition wall; wherein the first channel is connected in series with the outlet pipe of the desulfurization oxidation blower (3); Condensate bypass, the condensate bypass comprising: Water intake pipe (14) connecting the condensate main pipeline before the inlet of the last stage low-pressure heater and the inlet of the second channel. A return water pipeline (17) is connected between the outlet and return water position switching device (20) of the second channel; The return water position switching device (20) selectively returns the heated condensate to the condensate main pipeline at the outlet of the second-to-last low-pressure heater or the first-to-last low-pressure heater.

2. The high-pressure oxidation blower compression heat waste heat utilization system according to claim 1, characterized in that, The return water position switching device (20) includes: The first return water branch (20b) of the condensate main pipeline connecting the outlet of the return water pipeline (17) and the outlet of the first-stage low-pressure heater. The second return water branch (20a) of the condensate main pipeline connecting the outlet of the return water pipeline (17) and the outlet of the first second-stage low-pressure heater.

3. The high-pressure oxidation blower compression heat waste heat utilization system according to claim 2, characterized in that, The return water position switching device (20) further includes: on / off control valves respectively installed in the first return water branch (20b) and the second return water branch (20a).

4. The high-pressure oxidation blower compression heat waste heat utilization system according to claim 1, characterized in that, The water intake pipeline (14) is equipped with a flow distribution device for regulating flow rate. The flow distribution device distributes condensate to the last stage low-pressure heater and the condensate bypass.

5. The high-pressure oxidation blower compression heat waste heat utilization system according to claim 4, characterized in that, The flow distribution device regulates the condensate flow rate flowing into the condensate bypass to be no higher than 20% of the total flow rate of the main condensate pipeline at the water intake point.

6. The high-pressure oxidation blower compression heat waste heat utilization system according to claim 4, characterized in that, The flow distribution device includes: a third electric shut-off valve (29), an electric regulating valve (30) and a third manual shut-off valve (31) connected in series in the water intake pipeline (14), and a fourth manual shut-off valve (32) connected in parallel with the third electric shut-off valve (29), the electric regulating valve (30) and the third manual shut-off valve (31).

7. The high-pressure oxidation blower compression heat waste heat utilization system according to claim 4, characterized in that, The flow distribution device includes: a regulating three-way valve, which is connected to the inlet of the water intake pipeline (14), the inlet of the condensate main pipeline of the last stage low-pressure heater, and the condensate outlet.

8. The high-pressure oxidation blower compression heat waste heat utilization system according to claim 1, characterized in that, The multi-stage low-pressure heater includes: a first low-pressure heater (34) as the last stage low-pressure heater, a second low-pressure heater (35) as the first stage low-pressure heater, and a third low-pressure heater (36) as the second stage low-pressure heater.

9. A method for utilizing the waste heat from the compression of a high-pressure oxidation blower, used in the high-pressure oxidation blower waste heat utilization system according to any one of claims 1 to 8, characterized in that, include: Monitor the outlet air temperature of the oxidation blower (3) and the condensate outlet water temperature of the waste heat utilization heat exchanger (9); Based on the comparison results of the outlet air temperature of the oxidation blower (3) and / or the outlet water temperature of the waste heat utilization heat exchanger (9) and the corresponding preset threshold, the action of the return water position switching device is controlled to select to return the heated condensate to the outlet of the second-stage low-pressure heater or the first-stage low-pressure heater before the last-stage low-pressure heater.

10. The method for utilizing the waste heat from the compression of a high-pressure oxidation blower according to claim 9, characterized in that, The step of controlling the operation of the return water position switching device based on the comparison result of the outlet air temperature of the oxidation blower (3) and / or the outlet water temperature of the waste heat utilization heat exchanger (9) and the corresponding preset threshold, so as to select to return the heated condensate to the outlet of the second stage or the first stage low-pressure heater before the last stage low-pressure heater, includes: When the outlet air temperature of the oxidation blower (3) is higher than or equal to the first air temperature threshold, and / or the outlet water temperature of the waste heat utilization heat exchanger (9) is higher than or equal to the first water temperature threshold, the control return water switching device will return the condensate to the outlet of the first second stage low-pressure heater. When the outlet air temperature of the oxidation blower (3) is lower than the first air temperature threshold, and / or the outlet water temperature of the waste heat utilization heat exchanger (9) is lower than the first water temperature threshold, the control return water switching device will return the condensate to the outlet of the first stage low-pressure heater.

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