Gas-source-free automatic oxygen adding system for boiler feed water

Abstract

The utility model discloses an air-source-free automatic oxygen adding system for boiler feed water, which is characterized in that boiler feed water in a boiler feed water supply pipeline is sucked in through suction force generated at a water inlet end of a condensate pump when the condensate pump conveys condensate water, and the boiler feed water contains saturated dissolved oxygen and is uniform in oxygen content, so that the oxygen content of the boiler feed water is reduced; in addition, the boiler feed water is necessary to be supplied to the boiler, so that the boiler feed water is directly sucked by the condensate pump, namely, oxygen is added to the boiler feed water, and the conventional unpowered and gas-source-free automatic oxygen adding of the boiler feed water is realized; oxygen, compressed air, supersaturated dissolved oxygen demineralized water, a special water pump and the like which are usually needed by water supply oxygenation treatment are omitted, the operation cost of manpower and material resources is saved, the safety of water supply oxygenation is improved, in addition, due to the fact that part of make-up water is sucked into the negative pressure side of the condensate pump, the amount of make-up water sprayed into the condenser is reduced, and the energy consumption is reduced. Therefore, the vacuum-pumping burden of the condenser is relieved.

Description

Technical Field

[0001] The utility model belongs to the field of boiler feed water oxygenation systems, in particular to an automatic boiler feed water oxygenation system without a gas source. Background Art

[0002] The purpose of oxygenation in feed water treatment is to increase the redox potential of boiler feed water to an appropriate value, converting the ferroferric oxide on the metal surface of the feed water system into a high-valent hydrated ferric oxide with much lower solubility, thereby reducing the iron content of boiler feed water and inhibiting flow-accelerated corrosion (FAC) of the furnace system, especially the boiler economizer inlet pipe and high-pressure heater pipe.

[0003] The way to increase the redox potential of boiler feed water to an appropriate value is to add an appropriate amount of oxygen to the feed water. The main methods for achieving this are currently as follows: 1. Adding oxygen to condensate and feed water; 2. Adding compressed air to condensate and feed water; 3. Adding oxygen-rich desalted water to condensate and feed water.

[0004] The first method is also the most traditional method, which is to add oxygen to the condensate and feed water. This method requires the installation of automatic oxygenation devices for condensate and feed water, and has relatively high technical requirements for operation and maintenance. In addition, daily operation also requires the consumption of high-purity oxygen (purity above 99.9%), and the uniformity of dissolved oxygen is also relatively poor. It is necessary to purchase oxygen and frequently replace oxygen cylinders, which increases the workload of operators.

[0005] The second method has only emerged in recent years, which is to add compressed air to the condensate and feed water. Air is a mixed gas in the earth's atmosphere. It is a mixture, mainly composed of nitrogen, oxygen, rare gases (helium, neon, argon, krypton, xenon, radon), carbon dioxide and other substances (such as water vapor, impurities, etc.). The volume fraction of nitrogen is about 78%, the volume fraction of oxygen is about 21%, the volume fraction of rare gases (helium, neon, argon, krypton, xenon, radon) is about 0.934%, the volume fraction of carbon dioxide is about 0.04%, and the volume fraction of other substances (such as water vapor, impurities, etc.) is about 0.02%. The composition ratio of air changes with altitude and air pressure.

[0006] This method not only adds oxygen, but also adds impurity gases in the air to the water vapor system of the generator set. The harm of carbon dioxide impurities to the water vapor system of the generator set is recognized, and the impact of other impurities is still inconclusive. However, studies have shown that under supercritical conditions, nitrogen in steam has a certain nitriding effect on the inner surface of the metal pipe and has a certain impact on the mechanical properties of the metal. Therefore, all developed countries in the world have no precedent for adding air to the water vapor system of the generator set.

[0007] The third method is to add oxygen-rich desalted water to the condensate and feed water. This method also requires special equipment, and both operation and maintenance require relatively high technical requirements. In addition, daily operation also requires the consumption of high-purity oxygen (purity above 99.9%).

[0008] In addition, there is another method, which is to add oxygen (including oxygen-enriched desalted water and compressed air) to the drain side of the No. 1 high-pressure heater in addition to adding oxygen (including oxygen-enriched desalted water and compressed air) to the condensate and feed water, in order to solve the problem of fouling of the No. 1 high-pressure heater trap. However, the cause of the fouling of the No. 1 high-pressure heater trap is actually the high iron ion content of the heating steam, and the source is the flow-accelerated corrosion in the feed water system. All super (super) thermal power units that normally implement feed water oxygenation treatment no longer have the problem of flow-accelerated corrosion in their feed water systems, and the fouling of the No. 1 high-pressure heater trap no longer exists. Obviously, adding oxygen (including oxygen-enriched desalted water and compressed air) to the drain side of the No. 1 high-pressure heater is actually a meaningless measure. Utility Model Content

[0009] (1) Technical problem to be solved: The existing oxygenation methods using oxygen, compressed air, supersaturated dissolved oxygen desalted water and special water pumps require additional special power equipment and gas sources, which have relatively high manpower and material costs and their own shortcomings. The utility model provides a conventional unpowered and gas-free boiler feed water automatic oxygenation, which eliminates the oxygen, compressed air, supersaturated dissolved oxygen desalted water and special water pumps usually required for feed water oxygenation treatment, thereby saving manpower and material operating costs and improving the safety of feed water oxygenation.

[0010] (2) The technical solution adopted by the utility model is as follows:

[0011] A gas source-free boiler feed water automatic oxygenation system comprises a condensate pump connected to a condenser via a condensate intake pipeline, a water outlet of the condensate pump is connected to a condensate delivery pipeline, the condensate intake pipeline is connected to a boiler feed water supply pipeline, and a flow meter, a suction feed water flow regulating valve and a suction feed water stop valve are arranged on the boiler feed water supply pipeline.

[0012] A further technical solution is that a spare pipeline is connected to the boiler feed water supply pipeline, the flow meter on the boiler feed water supply pipeline is located before the spare pipeline, the spare pipeline is provided with a feed water spare pump, a spare flow regulating valve and a spare stop valve, the condensate water intake pipeline is provided with a condensate pump inlet valve at the water inlet end of the condensate pump, and the condensate water delivery pipeline is provided with a condensate pump outlet valve at the water outlet end of the condensate pump.

[0013] A further technical solution is that the boiler feed water supply pipeline is connected to the feed water tank, and a water tank outlet valve is arranged at the outlet of the feed water tank on the boiler feed water supply pipeline.

[0014] A further technical solution is that a bypass valve of a condensate polishing device is provided on the condensate conveying pipeline, and a condensate polishing device is provided on the condensate conveying pipeline in parallel with the bypass valve of the condensate polishing device.

[0015] A further technical solution is that the condensate delivery pipeline is connected in sequence to the low-pressure heater, the deaerator and the boiler high-pressure water feed system.

[0016] (3) Due to the adoption of the above technical solution, the beneficial effects of the utility model are:

[0017] By arranging a boiler feed water supply pipeline on the condensate water intake pipeline, and arranging a flow meter, an inhaled feed water flow regulating valve and an inhaled feed water stop valve on the boiler feed water supply pipeline, the boiler feed water in the boiler feed water supply pipeline can be sucked in by the suction force generated at the water inlet end of the condensate pump when the condensate pump conveys the condensate. Since the boiler feed water contains saturated dissolved oxygen and has a uniform oxygen content, and the boiler feed water itself is used to supply the boiler, the utility model directly uses the condensate pump to inhale the boiler feed water, which is equivalent to oxygenating the boiler feed water, realizing conventional automatic oxygenation of boiler feed water without power and air source, eliminating the oxygen, compressed air, supersaturated dissolved oxygen desalted water and special water pumps usually required for feed water oxygenation treatment, not only saving manpower and material operating costs, but also improving the safety of feed water oxygenation. In addition, since part of the feed water is inhaled into the negative pressure side of the condensate pump, the amount of feed water sprayed into the condenser is reduced, thereby reducing the burden of condenser vacuuming. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0019] Figure 2 It is a table of saturated dissolved oxygen content in boiler feed water at different temperatures. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0021] like Figure 1-Figure 2A boiler feed water automatic oxygenation system without gas source comprises a condensate pump 2 connected to a condenser 1 through a condensate intake pipeline 21, a water outlet of the condensate pump 2 is connected to a condensate delivery pipeline 3, a boiler feed water supply pipeline 4 is connected to the condensate intake pipeline 21, and a flow meter 5, a suction feed water flow regulating valve 6 and a suction feed water stop valve 7 are arranged on the boiler feed water supply pipeline 4.

[0022] When in use, the boiler feed water supply pipeline 4 is connected to the feed water tank 14, and a water tank outlet valve 15 is arranged at the outlet of the feed water tank 14 on the boiler feed water supply pipeline 4. The boiler feed water supply pipeline 4 is connected to a position close to the water inlet end of the condensate pump 2. The condensate of the condenser 1 is generally transported to the condensate polishing device 17 through the condensate pump 2. After the condensate is treated, it will return to the boiler. If it is necessary to add oxygen to the boiler feed water, the water tank outlet valve 15 and the suction feed water stop valve 7 are opened, and the boiler feed water will be sucked into the condensate pump 2 and finally supplied to the boiler along with the condensate. The flow regulating valve adjusts the suction flow of the saturated dissolved oxygen feed water according to a certain ratio according to the condensate flow of the unit. The premise of sucking an appropriate amount of saturated dissolved oxygen boiler feed water from the negative pressure measurement at the inlet of the condensate pump 2 is that there is no significant cooling water leakage in the condenser 1, that is, the hydrogen conductivity of the condensate is not greater than 0.15μS / cm (25°C).

[0023] The boiler feed water supply pipeline 4 is connected to a spare pipeline 8, and the flow meter 5 on the boiler feed water supply pipeline 4 is located before the spare pipeline 8. The spare pipeline 8 is provided with a feed water standby pump 9, a standby flow regulating valve 10 and a standby stop valve 11. The condensate water intake pipeline 21 is provided with a condensate pump inlet valve 12 at the water inlet end of the condensate pump 2, and the condensate water delivery pipeline 3 is provided with a condensate pump outlet valve 13 at the water outlet end of the condensate pump 2.

[0024] The backup pipeline 8 is provided in order to prevent the condensate quality from slightly exceeding the standard when there is cooling water leakage in the condenser 1, that is, when the hydrogen conductivity of the condensate is greater than 0.15 μS / cm (25°C), the suction feed water stop valve 7 can be closed at this time, and the boiler feed water is directly transported to the boiler feed water supply pipeline 4 by the feed water backup pump 9, without being transported through the condensate polishing device 17, and finally supplied to the boiler. Generally, a condensate sample is taken at the outlet of the condensate pump 2 to detect the hydrogen conductivity, and a sensor for detecting the hydrogen conductivity is usually provided. The sensor, flow meter 5, suction feed water flow regulating valve 6, suction feed water stop valve 7, water tank outlet valve 15, condensate pump 2, feed water backup pump 9, backup flow regulating valve 10, backup stop valve 11, condensate pump inlet valve 12, and condensate pump outlet valve 13 are all connected to the PLC-based automatic control system, and the upper limit of the hydrogen conductivity of the condensate is set to 0.15 μS / cm (25°C). When the hydrogen conductivity of the condensate is ≤0.15μS / cm (25°C), the suction feed water stop valve 7 opens automatically, and the flow rate of the saturated dissolved oxygen feed water is adjusted by the suction feed water flow regulating valve 6. When the hydrogen conductivity of the condensate is >0.15μS / cm (25°C), the suction feed water stop valve 7 closes automatically, and the feed water standby pump 9 starts automatically at the same time, the condensate pump 2 and the condensate pump outlet valve 13 are both closed, the standby stop valve 11 opens sequentially, and the standby flow regulating valve 10 adjusts the flow rate of the saturated dissolved oxygen feed water.

[0025] The condensate conveying pipeline 3 is provided with a condensate polishing device bypass valve 16, and a condensate polishing device 17 is provided in parallel with the condensate polishing device bypass valve 16 on the condensate conveying pipeline 3. The condensate polishing device 17 is a prior art for treating impurities in condensate. A condensate polishing device inlet valve 19 is provided before the condensate polishing device 17, and a condensate polishing device outlet valve 20 is provided after the condensate polishing device 17. After a certain flow of boiler feed water saturated with dissolved oxygen is sucked into the condensate, it is pumped into the condensate polishing device 17 together with the condensate by the condensate pump 2, and then enters the low-pressure water supply system, and after being heated by the low-pressure heater, enters the deaerator. When the spare pipeline is used, the condensate polishing device bypass valve 16 and the condensate polishing device outlet valve 20 are both in a closed state.

[0026] The condensate delivery pipeline 3 is connected to the shaft seal heater 18, the low-pressure heater, the deaerator and the boiler high-pressure feed water system in sequence, and an online dissolved oxygen meter is set at the deaerator inlet to detect the dissolved oxygen content. After the condensate and the boiler feed water are treated by the condensate polishing device 17, they enter the shaft seal heater 18 for heating (or the boiler feed water in the spare pipeline 8 directly enters the shaft seal heater 18 for heating), and then enter the deaerator. The dissolved oxygen content of the deaerator outlet water is controlled by adjusting the opening of the deaerator exhaust valve. The deaerator outlet water is pumped into the existing high-pressure feed water system through the pre-pump and the feed water pump, and enters the economizer after being heated by the high-pressure heater. The dissolved oxygen content of the deaerator outlet water is controlled to ensure that the dissolved oxygen content of the economizer inlet feed water is within the qualified range. The dissolved oxygen content of the deaerator outlet water must meet the requirements of the dissolved oxygen content of the economizer inlet feed water. The flow control valve 10 and the standby flow control valve 10 are controlled by PLC. The input signals of the calculation program set in the PLC include the condensate flow rate and the measured value of the online dissolved oxygen meter at the deaerator inlet, while the saturated dissolved oxygen content in the boiler feed water is determined at a certain ambient temperature (see Figure 2 ), the output signal for controlling the opening of the flow control valve can be obtained by calculation.

[0027] When the heating unit feed water volume exceeds the condensate oxygen inhalation feed water volume, the excess feed water shall be sprayed into condenser 1 through the condenser 1 atomizing device. Feed water rate = (feed water flow - heating steam flow) / main steam flow. When determining the output of the boiler feed water treatment system, the in-plant water vapor circulation loss of 600MW thermal power units is generally determined according to the regulations as 1.5% of the maximum continuous evaporation of the boiler, and the in-plant water vapor circulation loss of 1000MW thermal power units is determined as 1.0% of the maximum continuous evaporation of the boiler.

[0028] In the prior art, for thermal power units that use feed water oxygenation treatment, the dissolved oxygen in the feed water is removed, and then oxygen is added to the condensate and feed water, which is not only redundant, but also increases the burden of condenser vacuuming. The utility model reduces the amount of feed water sprayed into the condenser because part of the feed water is sucked into the negative pressure side of the condensate pump, thereby reducing the burden of condenser vacuuming. Generally, boiler feed water needs to be deoxygenated, which meets the technical requirements of thermal power units without oxygenation treatment. The utility model uses boiler feed water oxygenation to meet the technical requirements of feed water oxygenation treatment.

[0029] In addition, the flow rate of boiler feed water sucked into the inlet side of the condensate pump is easy to accurately measure and adjust, while the flow rate of gas sucked into the inlet side of the condensate pump is not easy to accurately measure and adjust, because air and oxygen are compressible, and water is an incompressible liquid. Generally, boiler feed water needs to be deoxygenated, which meets the technical requirements of thermal power units without oxygen treatment. The current scheme uses feed water to add oxygen, which meets the technical requirements of feed water oxygenation treatment.

[0030] The above are only preferred embodiments of the present invention.

Claims

1. A boiler feed water automatic oxygenation system without gas source, comprising a condensate pump (2) connected to a condenser (1) via a condensate intake pipeline (21), the outlet end of the condensate pump (2) being connected to a condensate delivery pipeline (3), characterized in that: The condensate water intake pipeline (21) is connected to a boiler feed water supply pipeline (4), and the boiler feed water supply pipeline (4) is provided with a flow meter (5), an intake feed water flow regulating valve (6) and an intake feed water stop valve (7).

2. The automatic oxygenation system for boiler feed water without gas source according to claim 1 is characterized in that: The boiler feed water supply pipeline (4) is connected to a spare pipeline (8), the flow meter (5) on the boiler feed water supply pipeline (4) is located before the spare pipeline (8), the spare pipeline (8) is provided with a feed water spare pump (9), a spare flow regulating valve (10) and a spare stop valve (11), the condensate water intake pipeline (21) is provided with a condensate water pump inlet valve (12) at the water inlet end of the condensate water pump (2), and the condensate water delivery pipeline (3) is provided with a condensate water pump outlet valve (13) at the water outlet end of the condensate water pump (2).

3. The automatic oxygenation system for boiler feed water without gas source according to claim 1, characterized in that: The boiler feed water supply pipeline (4) is connected to the feed water tank (14), and a water tank outlet valve (15) is provided on the boiler feed water supply pipeline (4) at the outlet of the feed water tank (14).

4. The automatic oxygenation system for boiler feed water without gas source according to claim 1, characterized in that: The condensate conveying pipeline (3) is provided with a condensate polishing device bypass valve (16), and the condensate polishing device (17) is provided on the condensate conveying pipeline (3) in parallel with the condensate polishing device bypass valve (16).

5. The automatic oxygenation system for boiler feed water without gas source according to claim 1, characterized in that: The condensate delivery pipeline (3) is sequentially connected to the shaft seal heater (18), the low-pressure heater, the deaerator and the boiler high-pressure feed water system.

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