Heating medium water drainage recovery system and method

Abstract

The invention relates to the technical field of drain recovery, and provides a heating medium water drain recovery system which comprises a drain flash tank, a low-pressure heater, a condenser, a deaerator and a drain pipeline. The drain flash tank and the low-pressure heater are both communicated with the condenser, and the condenser is communicated with the deaerator; the drain pipeline comprises a first drain pipe, a second drain pipe and a third drain pipe which are used for conveying drain water; one end of the first drain pipe is communicated with the steam heater, and the other end is communicated with the second drain pipe and the third drain pipe; the second drain pipe is communicated with the low-pressure heater, and the third drain pipe is communicated with the drain flash tank; the invention further discloses a heating medium water drainage recovery method. The drain water is conveyed to the low-pressure heater, heat of the drain water is recycled, and meanwhile the working stability of the drain water flash tank is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrophobic recovery, and in particular to a thermal medium water hydrophobic recovery system and method. Background Art

[0002] Ultra-low emissions of coal-fired units in thermal power plants are now mandatory. The main purpose is to reduce the emission concentrations of the main pollutants, smoke, sulfur dioxide and nitrogen oxides, of coal-fired generating units to no more than 5 mg / m 3 , 35mg / m 3 , 50mg / m 3 , reaching the emission level of gas units, the heat medium water is used to absorb the heat of the front flue gas to heat the tail flue gas, ensuring that the chimney exhaust temperature meets the chimney low-temperature corrosion and environmental impact assessment requirements. The heat medium water vapor heating is used to assist in heating the heat medium water when the heat of the front flue gas is insufficient. Its drainage design is particularly important in energy conservation and emission reduction of generator sets.

[0003] CN219494060U discloses a low-pressure heater drain recovery unit, including a common low-pressure drain tank, which is used to be connected to the first drain discharge pipeline of the first low-pressure heater group and the second drain discharge pipeline of the second low-pressure heater group; and a drain pump assembly, including a drain pump, an inlet pipeline and an outlet pipeline, the inlet of the drain pump is connected to the common low-pressure drain tank through the inlet pipeline, the outlet of the drain pump is connected to the outlet pipeline, the drain in the low-pressure drain tank enters the drain pump through the inlet pipeline, and the drain pump is used to pump the drain to the outlet pipeline for discharge.

[0004] CN116447892A discloses a steam drain recovery system, comprising a drain expansion tank, the drain expansion tank having an inlet, a first outlet and a second outlet, the inlet being used to communicate with a steam-flue gas heat exchanger so that saturated drain flowing out of the steam-flue gas heat exchanger flows into the drain expansion tank; a steam turbine, the steam turbine being communicated with the first outlet so that the extraction steam flowing out of the steam turbine merges with the steam flowing out of the drain expansion tank; an air preheater, the air preheater being communicated with the steam turbine and the drain expansion tank respectively so that the merged steam flows into the air preheater; and a deaerator, the deaerator being communicated with the second outlet so that the saturated water flowing out of the drain expansion tank flows into the deaerator.

[0005] At present, the original design of the heat medium steam heater drain is to drain to the atmospheric expansion tank on the furnace side, and then discharge into the unit drain tank. It can also be drained to the auxiliary steam drain expansion tank through a valve switch, and the working medium of the auxiliary steam drain expansion tank is recovered to the condenser; in the early operation, the heat medium steam heater drain is discharged to the atmospheric expansion tank on the furnace side, and the working medium water cannot be recovered and is wasted, which increases the pressure of desalted water preparation. Therefore, it is usually necessary to switch the heat medium steam heater drain to the auxiliary steam drain expansion tank through a valve and discharge it to the condenser.

[0006] The following problems exist when transferring the heat medium steam heater drain to the auxiliary steam drain expansion tank:

[0007] The load of the unit changes during operation, and the drain flow rate of the heat medium steam heater changes greatly. Since the design capacity of the auxiliary steam drain expansion tank is small, the water level of the drain expansion tank often fluctuates greatly, increasing the operation risk of the auxiliary steam drain expansion tank; at the same time, when the water level of the auxiliary steam drain expansion tank is high, the drain gate of the auxiliary steam drain expansion tank needs to be opened. When the drain gate from the auxiliary steam drain expansion tank to the condenser is not closed in time or the pipeline valve has internal leakage, it will affect the condenser vacuum, which is extremely risky; at the same time, the heat waste of the heat medium steam drain is serious during the transportation process, and condensate cooling is required to increase energy consumption. Summary of the invention

[0008] The current heat medium water recovery system has the following problems: the load changes during the operation of the unit, and the heat medium steam heater drain flow rate changes greatly. Since the design capacity of the auxiliary steam drain expansion tank is small, the water level of the drain expansion tank often fluctuates greatly, increasing the operation risk of the auxiliary steam drain expansion tank; at the same time, when the water level of the auxiliary steam drain expansion tank is high, the auxiliary steam drain expansion tank drain gate needs to be opened. When the auxiliary steam drain expansion tank to the condenser drain gate is not closed in time or the pipeline valve has internal leakage, it will affect the condenser vacuum, which is extremely risky; at the same time, the heat waste of the heat medium steam drain is serious during the transportation process, and condensate cooling is required to increase energy consumption.

[0009] In view of this, the present invention aims to provide a heat medium water drain recovery system. In the present invention, the heat medium water drain recovery system includes a drain expansion tank, a low-pressure heater, a condenser, a deaerator and a drain pipeline;

[0010] The drain expansion tank and the low-pressure heater are both in communication with the condenser, and the condenser is in communication with the deaerator;

[0011] The drain pipeline includes a first drain pipe, a second drain pipe and a third drain pipe for conveying drain; one end of the first drain pipe is connected to the steam heater, and the other end is connected to the second drain pipe and the third drain pipe; the second drain pipe is connected to the low-pressure heater, and the third drain pipe is connected to the drain expansion tank; the drain discharged from the steam heater can enter the low-pressure heater to heat the condensate in the low-pressure heater.

[0012] The drain is introduced into the low-pressure heater through the newly added second drain pipe, and the condensate in the low-pressure heater is heated by the heat of the drain, thereby realizing heat recovery of the drain. The drain is directly cooled by the condensate in the low-pressure heater, reducing the energy consumption of subsequent drain cooling and improving energy utilization.

[0013] Furthermore, the low-pressure heater is connected to the condenser through a fourth drain pipe, and the second drain pipe, the third drain pipe and the fourth drain pipe are all provided with regulating valves, which divide the drain delivery mode into a heat recovery mode, a water level adjustment mode and a cut-off mode;

[0014] In the heat recovery mode, the regulating valve on the second drain pipe is opened, the regulating valve on the third drain pipe is closed, and the regulating valve on the fourth drain pipe is opened;

[0015] In the water level adjustment mode, the regulating valve on the second drain pipe is opened, the regulating valve on the third drain pipe is closed, and the opening of the regulating valve on the fourth drain pipe is adjusted;

[0016] In the cut-off mode, the regulating valve on the second drain pipe is closed, and the regulating valve on the third drain pipe is opened.

[0017] Furthermore, the drain expansion tank is connected to the drainage tank of the unit through a sewage pipe, a water quality monitoring unit is provided on the second drain pipe, and the drain delivery mode also includes a sewage discharge mode;

[0018] When it is detected that the drain input into the second drain pipe is unqualified, the regulating valve on the second drain pipe is closed, the regulating valve on the third drain pipe is opened, and the pipeline connection between the drain expansion tank and the condenser is closed, and the regulating valve on the drain pipe is opened to discharge the drain directly to the unit drain tank.

[0019] Furthermore, a water treatment device is provided between the condenser and the deaerator.

[0020] Furthermore, the second drain pipe is inserted into the drain inlet pipe of the low-pressure heater at an angle of 45°.

[0021] Furthermore, a flushing water pipe is provided on the second drain pipe.

[0022] Furthermore, the heat medium water drain recovery system further comprises a water level regulating module, which can adjust the opening of the regulating valve on the fourth drain pipe according to the drain water level in the low-pressure heater;

[0023] The water level regulating module includes a water level sensor, a control unit and a driving unit;

[0024] The water level sensor is installed in the low-pressure heater to detect the water level of the drain in the low-pressure heater and transmit the detected water level value to the control unit;

[0025] The control unit is used to receive the water level value, calculate the opening of the regulating valve on the fourth drain pipe according to the water level value, and then control the operation of the driving unit according to the calculated opening;

[0026] The control unit is connected to the control unit and the regulating valve on the fourth drain pipe to control and adjust the opening of the regulating valve on the fourth drain pipe.

[0027] Furthermore, the first drain pipe and the second drain pipe are both provided with a pressure transmitter, a thermocouple and a flow meter.

[0028] The present invention also discloses a heat medium water drain recovery method, which is applicable to the above-mentioned heat medium water drain recovery system, comprising:

[0029] Step S1, first flush the drain pipe, and test the drain through a water quality monitoring unit, and check if it is qualified;

[0030] Step S2, opening the regulating valve on the second drain pipe, closing the regulating valve on the third drain pipe, opening the regulating valve on the fourth drain pipe, and recycling the drain to the low-pressure heater to heat the condensate in the low-pressure heater;

[0031] Step S3, real-time monitoring of the water level of the drain in the low-pressure heater, and adjusting the water level of the drain in the low-pressure heater by a water level regulating module, so that the water level of the drain in the low-pressure heater always meets the requirements;

[0032] Step S4, monitoring the water quality of the drain in the drain pipeline by a water quality monitoring unit. When the water quality is unqualified, closing the regulating valve on the second drain pipe, opening the regulating valves on the third drain pipe and the sewage pipe, and draining the drain to the drainage tank of the unit;

[0033] Step S5, draining the drain water after heat recovery in the low-pressure heater into the condenser, and recovering it after fine treatment.

[0034] Further, regulating the water level of the drain in the low-pressure heater by the water level regulating module includes:

[0035] Obtaining a real-time water level value of the drain in the low-pressure heater, presetting a water level threshold, and comparing the real-time water level value with the water level threshold;

[0036] When the real-time water level value is greater than the water level threshold, the opening of the regulating valve on the fourth drain pipe is increased to speed up the discharge rate of the drain in the low-pressure heater and reduce the water level in the low-pressure heater;

[0037] At the same time, a water level difference between the real-time water level value and the water level threshold is calculated, and the opening of the regulating valve of the fourth drain pipe is calculated according to the water level difference.

[0038] The heat medium water drain system disclosed in the present invention improves the drain pipeline, introduces drain into the low-pressure heater through a newly added second drain pipe, heats the condensate in the low-pressure heater through the heat of the drain, realizes heat recovery of the drain, and directly cools the drain through the condensate in the low-pressure heater, reduces the energy consumption of subsequent drain cooling, and improves the energy utilization rate; at the same time, since the drain is introduced into the low-pressure heater, the drain will be discharged into the drain expansion tank only when the drain water level in the low-pressure heater is high and difficult to control through the water level regulating module, which greatly reduces the flow rate of drain in the drain expansion tank, avoids the situation that the water level in the drain expansion tank often shakes greatly and the vacuum is affected by the need to drain when the water level is high, and greatly improves the stability of the operation of the drain expansion tank.

[0039] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0041] Figure 1 A schematic diagram of the connection structure of a drain pipe in one embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the connection structure of the hydrophobic expansion container in one embodiment of the present invention;

[0043] Figure 3 Schematic diagram of the connection structure of a deaerator in one embodiment of the present invention.

[0044] Description of reference numerals:

[0045] 1. Drain expansion tank; 2. Low-pressure heater; 3. Deaerator; 4. First drain pipe; 5. Second drain pipe; 6. Third drain pipe; 7. Sampling pipe; 8. Flushing water pipe; 9. Fourth drain pipe. DETAILED DESCRIPTION

[0046] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0047] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices; "fixed" or "fixed connection" generally refers to common mechanical connection methods, such as threaded connection, welding or bonding, etc.

[0049] In the prior art, the heat medium steam heater drain is originally designed to drain to the furnace side atmospheric expansion tank, and then discharged into the unit drain tank. It can also be drained to the auxiliary steam drain expansion tank 1 through a valve switch, and the working medium of the auxiliary steam drain expansion tank 1 is recovered to the condenser; in the early operation, the heat medium steam heater drain is discharged to the furnace side atmospheric expansion tank, and the working medium water cannot be recovered and is wasted, which increases the pressure of desalted water preparation. Therefore, it is usually necessary to switch the heat medium steam heater drain to the auxiliary steam drain expansion tank 1 through a valve and discharge it to the condenser.

[0050] At present, the above-mentioned heat medium water recovery system has the following problems: the load of the unit changes during operation, and the drain flow rate of the heat medium steam heater changes greatly. Since the design capacity of the auxiliary steam drain expansion tank 1 is small, the water level of the drain expansion tank 1 often shakes greatly, increasing the operation risk of the auxiliary steam drain expansion tank 1; at the same time, when the water level of the auxiliary steam drain expansion tank 1 is high, the drain gate of the auxiliary steam drain expansion tank 1 needs to be opened. When the drain gate from the auxiliary steam drain expansion tank 1 to the condenser is not closed in time or the pipeline valve has a loose internal leakage, it will affect the condenser vacuum, which is very risky; at the same time, the heat waste of the heat medium steam drain is serious during the transportation process, and condensate cooling is required to increase energy consumption.

[0051] The present invention provides a heat medium water drainage recovery system, such as Figure 1 , Figure 2 and Figure 3 As shown, in this embodiment, the heat medium water drain recovery system includes a drain expansion tank 1, a low-pressure heater 2, a condenser, a deaerator 3 and a drain pipeline; the drain expansion tank 1 and the low-pressure heater 2 are both connected to the condenser, and the condenser is connected to the deaerator 3.

[0052] The drain pipeline includes a first drain pipe 4, a second drain pipe 5 and a third drain pipe 6 for conveying drain; one end of the first drain pipe 4 is connected to the steam heater, and the other end is connected to the second drain pipe 5 and the third drain pipe 6; the second drain pipe 5 is connected to the low-pressure heater 2, and the third drain pipe 6 is connected to the drain expansion tank 1; the drain discharged from the steam heater can enter the low-pressure heater 2 to heat the condensate in the low-pressure heater 2; the first drain pipe 4 and the second drain pipe 5 are both provided with a pressure transmitter, a thermocouple and a flow meter for monitoring the drain pressure, drain temperature and drain flow in the drain pipeline; in this embodiment, the low-pressure heater is arranged in multiple groups, and the multiple groups of low-pressure heaters are connected in sequence, and the drain is introduced into the multiple groups of low-pressure heaters in sequence, and the drain is introduced into the subsequent low-pressure heaters for step-by-step heat recovery after heat recovery from one group of low-pressure heaters, and the introduction end, i.e., the connection end of the second drain pipe, is close to the low-pressure heater to reduce the pressure loss of the connecting pipeline.

[0053] Since the heat of the hydrophobic gas cannot be fully recovered after being recovered by a low-pressure heater, the energy of the hydrophobic gas discharged from the low-pressure heater can still be recycled. Therefore, the hydrophobic gas is introduced into multiple groups of low-pressure heaters in turn for step-by-step recovery to ensure full heat recovery and save energy and resources.

[0054] In order to ensure the stability of drain transportation, ensure the stability of the drain water level in the low-pressure heater 2, and avoid the influence of the excessive water level in the low-pressure heater 2 on the low-pressure heater 2; the low-pressure heater 2 is connected to the condenser through the fourth drain pipe 9, and regulating valves are arranged on the second drain pipe 5, the third drain pipe 6 and the fourth drain pipe 9. The regulating valves adjust the opening and closing of the second drain pipe 5, the third drain pipe 6 and the fourth drain pipe 9, and divide the drain transportation mode into heat recovery mode, water level adjustment mode and cut-off mode. When the drain water level in the low-pressure heater 2 is normal, it is in heat recovery mode, and the heat of the drain is recovered normally. When the drain water level in the low-pressure heater 2 is too high, the drain transportation mode enters the water level adjustment mode, and the drain water level in the low-pressure heater 2 is adjusted. When the drain water level in the low-pressure heater 2 is too high and the drain discharge volume of the fourth drain pipe cannot be adjusted To control the water level of the drain in the low-pressure heater, the drain delivery mode enters the cut-off mode; in the heat recovery mode, the regulating valve on the second drain pipe 5 is opened, the regulating valve on the third drain pipe 6 is closed, and the regulating valve on the fourth drain pipe is opened with a small opening; in the water level adjustment mode, the regulating valve on the second drain pipe 5 is opened, the regulating valve on the third drain pipe 6 is closed, and the opening of the regulating valve on the fourth drain pipe is adjusted. Generally, the opening is increased when the water level is too high, and the opening is reduced when the water level is low; in the cut-off mode, that is, when the fourth drain valve is opened to the maximum and still cannot control the water level in the low-pressure heater to drop, the regulating valve of the second drain pipe is closed, the drain is stopped from continuing to be delivered to the low-pressure heater, and the low-pressure heater is controlled to only lower the water level in the drainage state, and at the same time, the regulating valve on the third drain pipe is opened to discharge all the drain to the drain expansion tank.

[0055] It should be noted that in the cut-off mode, when the water level in the low-pressure heater returns to normal, the heat recovery mode is switched back to perform normal drain heat recovery work; in this embodiment, the regulating valves on the second drain pipe and the third drain pipe are set as manual partition doors, and the opening and closing work is manually controlled by the staff, and the regulating valve on the fourth drain pipe is set as an electric regulating valve for mechanical control to facilitate precise adjustment of the opening.

[0056] The present invention improves the drain pipeline, introduces drain into the low-pressure heater 2 through the newly added second drain pipe 5, heats the condensed water in the low-pressure heater 2 through the heat of the drain, realizes heat recovery of the drain, and directly cools the drain through the condensed water in the low-pressure heater 2, reduces the energy consumption of subsequent drain cooling, and improves the energy utilization rate; at the same time, since the drain is introduced into the low-pressure heater 2, the drain will be discharged into the drain expansion tank 1 only when the drain water level in the low-pressure heater 2 is high and difficult to control through the water level regulating module, which greatly reduces the flow rate of drain in the drain expansion tank 1, avoids the situation that the water level of the drain expansion tank 1 often shakes greatly and the vacuum is affected by the need to drain when the water level is high, and greatly improves the stability of the operation of the drain expansion tank 1.

[0057] In order to ensure the cleanliness of the pipeline, a flushing water pipe 8 is provided on the second drain pipe 5 to flush the pipeline before the drain is discharged.

[0058] In order to ensure that the drain entering the low-pressure heater 2 has sufficient cleanliness and does not pollute the low-pressure heater 2 and subsequent pipelines, when the water quality pollution is too high, the drain is cut off to the low-pressure heater 2, the heat recovery of the drain is switched, and the drain is directly discharged into the unit drain tank after passing through the drain expansion tank 1. The specific settings are as follows: the drain expansion tank 1 is connected to the unit drain tank through a sewage pipe to ensure that the drain has a direct discharge path, and a water quality monitoring unit is provided on the second drain pipe 5 to monitor the water quality of the drain transported therein, and the drain transport mode also includes a sewage mode; the sewage mode is when it is detected that the drain input into the second drain pipe 5 is unqualified. In this embodiment, when the concentration of hydrophobic iron ions is higher than 500μg / L, it is determined that the water quality of the drain is unqualified. At this time, the regulating valve on the second drain pipe 5 is closed, the regulating valve on the third drain pipe 6 is opened, and the pipeline connection between the drain expansion tank 1 and the condenser is closed, and the regulating valve on the sewage pipe is opened to discharge the input drain directly into the unit drain tank.

[0059] Regarding the water quality monitoring unit, the present invention is provided with a sampling tube 7 connected to the second drain pipe, and the drain in the second drain pipe is collected from the sampling tube 7 manually or by machine at regular intervals for water quality monitoring; in other embodiments, the water quality monitoring unit may be provided with other structures; sampling is performed to detect the water quality when flushing the water pipe, and sampling is stopped when the water quality is qualified. However, in order to avoid the subsequent entry of sewage into the low-pressure heater, the water quality is monitored regularly to ensure the stability of the operation of the low-pressure heater.

[0060] In order to ensure the cleanliness of the recycled water and meet the subsequent boiler recycling requirements, a water treatment device is installed between the condenser and the deaerator 3 to perform fine treatment on the recycled water before it enters the deaerator 3, thereby providing protection for the recycled water and avoiding recycling of contaminated water.

[0061] The drainage flow path of the present invention is as follows: the steam heater drainage enters the low-pressure heater 2 or the drainage expansion tank 1 through the drainage pipeline, then enters the condenser to wash out the impurities and harmful substances in the water, then passes through the water treatment device to perform fine treatment on the water to remove the remaining impurities, the finely treated water enters the deaerator 3 to remove the oxygen and other gases dissolved in the water, and finally is recovered to the boiler for recycling.

[0062] In order to reduce the resistance and eddy current of the newly added second drain pipe 5 when inserted into the parallel flow, and reduce the influence and disturbance of the drain on the water flow in the inserted pipe; the second drain pipe 5 is inserted into the drain inlet pipe of the low-pressure heater 2 at an angle of 45°, so as to reduce the pressure loss of the pipe and improve the stability of the drain entering the low-pressure heater 2; in actual application, the original flow velocity of the drain pipe of the low-pressure heater 2 is 1.5m / s, and now the flow velocity of the drain pipe after the second drain pipe 5 is incorporated is 1.73m / s, and the flow velocity is slightly increased, but it is still in a stable and reasonable range. Therefore, it is feasible to introduce the steam of the heat medium water into the connecting pipe of the low-pressure heater, and it will not affect the pipe of the low-pressure heater.

[0063] In order to conveniently and accurately adjust the water level of the drain in the low-pressure heater 2 and ensure the stable operation of the low-pressure heater, the discharge rate of the drain from the low-pressure heater is adjusted by controlling the opening of the regulating valve on the fourth drain pipe 9, and the water level of the low-pressure heater is controlled by the rate of drain discharge; a water level regulating module is set, which can adjust the opening of the regulating valve on the fourth drain pipe 9 according to the drain water level in the low-pressure heater 2; specifically, a water level boundary is set, and when the water level in the low-pressure heater is higher than the water level boundary, the water level is started The regulating module calculates the difference between the actual water level and the water level boundary, and adjusts the opening of the regulating valve on the fourth drain pipe 9 according to the size of the difference. The larger the difference is, the larger the opening of the regulating valve on the fourth drain pipe is, and the greater the discharge rate of the drain inside the low-pressure heater is. Therefore, the drain in the low-pressure heater 2 will be reduced, thereby reducing the drain water level in the low-pressure heater 2; conversely, when the water level in the low-pressure heater is low, the opening of the regulating valve on the fourth drain pipe is reduced, so that the water level in the low-pressure heater is always maintained in a stable state within a certain boundary.

[0064] Specifically: the water level regulating module includes a water level sensor, a control unit and a driving unit. The water level sensor is installed in the low-pressure heater 2 to detect the water level of the drain in the low-pressure heater 2, and transmits the detected water level value to the control unit; the control unit is used to receive the water level value, and calculate the opening of the regulating valve on the third drain pipe 6 according to the water level value, and then control the operation of the driving unit according to the calculated opening; the control unit is connected to the control unit and the regulating valve on the third drain pipe 6 to control and adjust the opening of the regulating valve on the third drain pipe 6. In this embodiment, the driving unit can adjust the regulating valve of the third drain pipe by electric control driven by a motor, start-up control driven by air pressure, hydraulic control driven by hydraulic pressure, etc., mainly based on automatic control and regulation.

[0065] The present invention also discloses a heat medium water drain recovery method, which is applicable to the above-mentioned heat medium water drain recovery system, comprising:

[0066] Step S1, first flush the drain pipe through the flushing water pipe 8, and detect the drain through the water quality monitoring unit to ensure that the drain through the second drain pipe meets the requirements;

[0067] Step S2, opening the regulating valve on the second drain pipe 5, closing the regulating valve on the third drain pipe 6, opening the regulating valve on the fourth drain pipe, and recycling the drain water to the low-pressure heater 2 to heat the condensate in the low-pressure heater 2;

[0068] Step S3, real-time monitoring of the water level of the drain in the low-pressure heater 2, and adjusting the water level of the drain in the low-pressure heater 2 by a water level regulating module, so that the water level of the drain in the low-pressure heater 2 always meets the requirements;

[0069] Step S4, monitoring the water quality of the hydrophobic water in the hydrophobic pipeline by a water quality monitoring unit. When the water quality is unqualified, that is, when the hydrophobic iron ion concentration is higher than 500 μg / L, close the regulating valve on the second hydrophobic pipe 5, open the regulating valve on the third hydrophobic pipe 6 and the drain pipe, and drain the hydrophobic water to the unit drain tank;

[0070] Step S5, draining the drain water after heat recovery in the low-pressure heater 2 into the condenser, and recovering it after fine treatment.

[0071] Wherein, regulating the water level of the drain in the low-pressure heater 2 by the water level regulating module includes:

[0072] Obtain the real-time water level value of the drain in the low-pressure heater 2, preset a water level threshold, and compare the real-time water level value with the water level threshold;

[0073] When the real-time water level value is greater than the water level threshold, the regulating valve of the fourth drain pipe 9 is opened, the opening of the regulating valve on the fourth drain pipe is increased, the discharge rate of the drain in the low-pressure heater is accelerated, and the water level in the low-pressure heater is reduced;

[0074] At the same time, the water level difference between the real-time water level value and the water level threshold is calculated, and the opening of the regulating valve of the fourth drain pipe 9 is calculated according to the water level difference.

[0075] On the contrary, when the water level in the low-pressure heater is low, the opening of the regulating valve on the fourth drain pipe is reduced so that the water level in the low-pressure heater is always maintained in a stable state within a certain limit, meeting normal recovery requirements.

[0076] Through the above-mentioned drain recovery method, the drain is introduced into the low-pressure heater for heat recovery, and the step of cooling the drain itself is eliminated. The drain is recovered, energy is saved and emissions are reduced, and the stability of the drain expansion tank is ensured. The water level of the drain in the low-pressure heater is automatically calculated to automatically adjust the drainage rate of the low-pressure heater, which makes the work convenient and the safety improved.

[0077] The idea of ​​the present invention is to discharge the drain of the heat medium water heater into the low-pressure heater for heat recovery, and to stabilize the water level of the drain in the low-pressure heater by adjusting the discharge rate of the drain. When it is still difficult to ensure the water level in the low-pressure heater by adjusting the drain discharge rate, a drain expansion tank is used as an auxiliary equipment to ensure the water level in the low-pressure heater, so as to recover heat and improve the safety of the operation of the drain expansion tank.

[0078] Take a generator set in a power plant as an example, based on the annual operating hours of the unit of 6500h, the unit price of standard coal is 1200 yuan / ton, and the thermal diagram of 75% THA condition is used for calculation:

[0079] There are three low-pressure heaters in the generator set, namely No. 6 LP heater, No. 7 LP heater and No. 8 LP heater. The heat medium water is first introduced into No. 6 LP heater for heat recovery, and then passes through No. 7 LP heater and No. 8 LP heater for heat recovery, and finally flows into the condenser; the data values ​​under 75% THA conditions are as follows:

[0080] Thermal medium water drainage: flow rate 10t / h, temperature 100.3℃, pressure 0.1MPa, enthalpy 420.33kj / kg;

[0081] Extraction steam of No. 6 low-pressure heater: flow rate 51.463t / h, temperature 147℃, pressure 0.108MPa, enthalpy 2769.2kj / kg;

[0082] No. 6 low-pressure drain: flow rate 105.853t / h, temperature 74.42℃, enthalpy value 311.5kj / kg;

[0083] Extraction steam of No. 7 low-pressure heater: flow rate 27.439t / h, temperature 72.8℃, pressure 0.033MPa, enthalpy 2586.3kj / kg;

[0084] No. 7 low-pressure drain: flow rate 133.292t / h, temperature 58.16℃, enthalpy value 243.4kj / kg;

[0085] Extraction steam of No. 8 low-pressure heater: flow rate 31.388t / h, temperature 56.5℃, pressure 0.016MPa, enthalpy 2488.6kj / kg;

[0086] No. 8 low-pressure drain: flow rate 164.68t / h, temperature 39.14℃, enthalpy value 163.9kj / kg;

[0087] Condenser exhaust: flow rate 807.553t / h, enthalpy value 2366.8kj / kg;

[0088] After the unit drain is transformed and recycled, the annual increase in power generation is calculated as follows:

[0089] The steam extraction displacement of No. 6 low-pressure heater t1 = heat medium water drainage × (heat medium water drainage enthalpy value - No. 6 low-pressure heater drainage enthalpy value) / (No. 6 low-pressure heater extraction enthalpy value - No. 6 low-pressure heater drainage enthalpy value) = 10t / h × (420.33kJ / kg-311.5kJ / kg) / (2769.2kJ / kg-311.5kJ / kg) = 0.443t / h

[0090] The steam extraction displacement of No. 7 low-pressure heater t2 = (heat medium water drainage volume - No. 6 low-pressure heater extraction displacement t1) × (No. 6 low-pressure heater drainage enthalpy value - No. 7 low-pressure heater drainage enthalpy value) / (No. 7 low-pressure heater extraction enthalpy value - No. 7 low-pressure heater drainage enthalpy value) = (10t / h-0.443t / h) × (311.5kJ / kg-243.4kJ / kg) / (2586.3kJ / kg-243.4kJ / kg) = 0.278t / h

[0091] The steam extraction displacement of No. 8 low-pressure heater t3 = (heat medium water drainage volume - the steam extraction displacement volume of No. 6 low-pressure heater t1 - the steam extraction displacement volume of No. 7 low-pressure heater t2) × (the drainage enthalpy value of No. 7 low-pressure heater - the drainage enthalpy value of No. 8 low-pressure heater) / (the extraction enthalpy value of No. 8 low-pressure heater - the drainage enthalpy value of No. 8 low-pressure heater) = (10t / h-0.443t / h-0.278t / h) × (243.3kJ / kg-163.9kJ / kg) / (2488.6kJ / kg-163.9kJ / kg) = 0.317t / h

[0092] Hourly additional power P = No. 6 low-pressure heater extraction steam displacement t1 × (No. 6 low-pressure heater extraction steam enthalpy value - condenser exhaust steam enthalpy value) / 3600 + No. 7 low-pressure heater extraction steam displacement t2 × (No. 7 low-pressure heater extraction steam enthalpy value - condenser exhaust steam enthalpy value) / 3600 + No. 8 low-pressure heater extraction steam displacement t3 × (No. 8 low-pressure heater extraction steam enthalpy value - condenser exhaust steam enthalpy value) / 3600 = 49.497kW + 16.938kW + 10.737kW = 77.171kW

[0093] Annual additional power generation E = hourly additional power P × annual operating hours of the unit = 77.171kW × 6500h = 501610.665kWh

[0094] Equivalent standard coal quantity T = annual power generation E × standard coal consumption = (501610.665kWh × 292g / kWh) / 1000000 = 146.47t

[0095] Annual total savings = equivalent standard coal quantity T × standard coal unit price = 146.47t × 1200 yuan / t = 175764.377 yuan

[0096] Therefore, it can be obtained that after the drain pipeline modification of this scheme, the annual power generation of the generator set is 501610.665kWh, the annual standard coal saving is 146.47t, and the annual total saving is 175764.377 yuan. It can be seen that this scheme has a great contribution to energy conservation and emission reduction of the generator set, and after calculation, the modification cost is about 5,000 yuan, which can be recovered in a short time.

[0097] In addition, the drain recovery system disclosed in the present invention is not limited to the heat medium water heater drain, but is also applicable to the use of urea hydrolyzer drain, urea hydrolysis zone drain tank drain, ash hopper heater drain and other units in the power plant.

[0098] In another embodiment of the present invention, the present invention also adopts another method for regulating the water level of the low-pressure heater; specifically: an electric regulating valve is set for the regulating valve on the third drain pipe, and the opening of the regulating valve on the fourth drain pipe is changed to adjusting the opening of the regulating valve on the third drain pipe, that is, the water level is adjusted by adjusting the drainage rate of the low-pressure heater instead of adjusting the drain flow entering the low-pressure heater.

[0099] When the water level in the low-pressure heater is normal, close the regulating valve on the third drain pipe. When the water level in the low-pressure heater is high, open the regulating valve on the third drain pipe to divert the drain part to the drain expansion tank, reduce the drain flow entering the low-pressure heater, thereby reducing the drain water level in the low-pressure heater. When the water level is high, increase the opening of the regulating valve on the third drain pipe to increase the flow diverted to the drain expansion tank.

[0100] When the regulating valve on the third drain pipe is opened, the pressures in the second drain pipe and the third drain pipe are different. In order to prevent the material in the drain expansion tank from flowing back into the low-pressure heater, a one-way valve is installed on the third drain pipe to ensure the vacuum state in the low-pressure heater and the subsequent condenser.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heat medium water drain recovery system, characterized in that: It comprises a drain expansion tank (1), a low-pressure heater (2), a condenser, a deaerator (3) and a drain pipeline; The hydrophobic expansion tank (1) and the low-pressure heater (2) are both connected to the condenser, and the condenser is connected to the deaerator (3); The drain pipeline comprises a first drain pipe (4), a second drain pipe (5) and a third drain pipe (6) for conveying drain; one end of the first drain pipe (4) is connected to the steam heater, and the other end is connected to the second drain pipe (5) and the third drain pipe (6); the second drain pipe (5) is connected to the low-pressure heater (2), and the third drain pipe (6) is connected to the drain expansion tank (1); the drain discharged from the steam heater can enter the low-pressure heater (2) to heat the condensate in the low-pressure heater (2).

2. The heat medium water drain recovery system according to claim 1, characterized in that: The low-pressure heater (2) is connected to the condenser via a fourth drain pipe (9); the second drain pipe (5), the third drain pipe (6) and the fourth drain pipe (9) are all provided with regulating valves, which divide the drain delivery mode into a heat recovery mode, a water level adjustment mode and a cut-off mode; In the heat recovery mode, the regulating valve on the second drain pipe (5) is opened, the regulating valve on the third drain pipe (6) is closed, and the regulating valve on the fourth drain pipe (9) is opened; In the water level adjustment mode, the regulating valve on the second drain pipe (5) is opened, the regulating valve on the third drain pipe (6) is closed, and the opening of the regulating valve on the fourth drain pipe (9) is adjusted; In the cut-off mode, the regulating valve on the second drain pipe (5) is closed, and the regulating valve on the third drain pipe (6) is opened.

3. The heat medium water drain recovery system according to claim 2, characterized in that: The drain expansion tank (1) is connected to the drainage tank of the unit through a sewage pipe, and a water quality monitoring unit is arranged on the second drain pipe (5), and the drain conveying mode also includes a sewage discharge mode; When it is detected that the drain water input into the second drain pipe (5) is unqualified, the regulating valve on the second drain pipe (5) is closed, the regulating valve on the third drain pipe (6) is opened, and the pipeline connection between the drain expansion tank (1) and the condenser is closed, and the regulating valve on the drain pipe is opened to discharge the drain water directly into the unit drain tank.

4. The heat medium water drain recovery system according to any one of claims 1 to 3, characterized in that: A water treatment device is provided between the condenser and the deaerator (3).

5. The heat medium water drain recovery system according to any one of claims 1 to 3, characterized in that: The second drain pipe (5) is inserted into the drain inlet pipe of the low-pressure heater (2) at an angle of 45°.

6. The heat medium water drain recovery system according to any one of claims 1 to 3, characterized in that: The second drain pipe (5) is provided with a flushing water pipe (8).

7. The heat medium water drain recovery system according to claim 2 or 3, characterized in that: The heat medium water drain recovery system further comprises a water level regulating module, wherein the water level regulating module is capable of regulating the opening of the regulating valve on the fourth drain pipe (9) according to the drain water level in the low-pressure heater (2); The water level regulating module includes a water level sensor, a control unit and a driving unit; The water level sensor is installed in the low-pressure heater (2) to detect the water level of the drainage in the low-pressure heater (2) and transmit the detected water level value to the control unit; The control unit is used to receive the water level value, calculate the opening of the regulating valve on the fourth drain pipe (9) according to the water level value, and then control the operation of the driving unit according to the calculated opening; The control unit is connected to the control unit and the regulating valve on the fourth drain pipe (9) to control and adjust the opening of the regulating valve on the fourth drain pipe (9).

8. The heat medium water drain recovery system according to any one of claims 1 to 3, characterized in that: The first drain pipe (4) and the second drain pipe (5) are both provided with a pressure transmitter, a thermocouple and a flow meter.

9. A method for recovering heat transfer water drain, applicable to the heat transfer water drain recovery system as claimed in claim 1, characterized in that: include: Step S1, first flush the drain pipe, and test the drain through a water quality monitoring unit, and check if it is qualified; Step S2, opening the regulating valve on the second drain pipe (5), closing the regulating valve on the third drain pipe (6), opening the regulating valve on the fourth drain pipe (9), and recycling the drain to the low-pressure heater (2) to heat the condensate in the low-pressure heater (2); Step S3, real-time monitoring of the water level of the drain in the low-pressure heater (2), and adjusting the water level of the drain in the low-pressure heater (2) by means of a water level regulating module, so that the water level of the drain in the low-pressure heater (2) always meets the requirements; Step S4, monitoring the water quality of the drain in the drain pipeline by means of a water quality monitoring unit. When the water quality is unqualified, closing the regulating valve on the second drain pipe (5), opening the regulating valves on the third drain pipe (6) and the drain pipe, and draining the drain to the drainage tank of the unit; Step S5, draining the drain water after heat recovery in the low-pressure heater (2) into the condenser, and recovering it after fine treatment.

10. The method for recovering heat medium water hydrophobicity according to claim 9, characterized in that: The step of regulating the water level of the drain in the low-pressure heater (2) by means of the water level regulating module comprises: Obtaining a real-time water level value of the drain in the low-pressure heater (2), presetting a water level threshold, and comparing the real-time water level value with the water level threshold; When the real-time water level value is greater than the water level threshold, the opening of the regulating valve on the fourth drain pipe (9) is increased to speed up the discharge rate of the drain in the low-pressure heater (2) and reduce the water level in the low-pressure heater (2); At the same time, the water level difference between the real-time water level value and the water level threshold is calculated, and the opening of the regulating valve of the fourth drain pipe (9) is calculated according to the water level difference.

Images