Negative pressure deoxygenation system and process

Abstract

The application discloses a negative pressure deoxygenation system and process, and belongs to the technical field of desalted water deoxygenation. The system comprises a heating system, a deoxygenation system and a vacuum pumping unit connected in sequence, wherein the vacuum pumping unit comprises two-stage vacuum pumping units connected in series. That is, according to the temperature of the desalted water into the deoxygenator, the liquid series vacuum pumping process is used to realize the control of the vacuum degree inside the deoxygenator, so that the dissolved oxygen and other gases are effectively removed. On the basis of ensuring the deoxygenation qualification, the energy consumption and water vapor loss are reduced compared with the existing steam stripping.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of salt water deoxygenation, and more particularly to a negative pressure deoxygenation system and process. BACKGROUND

[0002] The traditional thermal deaerator is a widely used deoxygenation mode in the industry, and the principle is to remove dissolved oxygen and CO and other gases according to the gas dissolution law, and to use steam to achieve the purpose of deoxygenation, but the steam consumption is large, the energy consumption is high, and the problem of excessive dissolved oxygen is serious.

[0003] Therefore, it is an urgent problem for those skilled in the art to provide a new negative pressure deoxygenation system and process for improving the dissolved oxygen qualification rate of a thermal deaerator, saving energy consumption and reducing steam consumption. SUMMARY

[0004] Therefore, the present application provides a new negative pressure deoxygenation system and process, which uses the principle of Henry's law and adopts a two-stage series liquid vacuum extraction process to form a high vacuum inside the equipment to change the partial pressure of softened water, thereby achieving the purpose of deoxygenation of low-temperature softened water.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A negative pressure deoxygenation system, comprising a heating system, a deoxygenation system and a vacuum extraction system connected in sequence;

[0007] The heating system comprises a heating furnace;

[0008] The deoxygenation system comprises a deaerator, a deoxygenation head and an N2 stripping distributor;

[0009] The heating system is connected to the deoxygenation head;

[0010] The deoxygenation head is fixed to the top of the deaerator;

[0011] The N2 stripping distributor is located at the bottom of the inner cavity of the deaerator;

[0012] The vacuum extraction system comprises a first-stage vacuum extraction unit and a second-stage vacuum extraction unit, which are connected in series;

[0013] The first-stage vacuum extraction unit comprises a first-stage ejector, a circulating liquid first-stage storage tank, a first-stage vacuum extraction circulating pump and a first-stage cooler connected in sequence;

[0014] The second-stage vacuum extraction unit comprises a second-stage ejector, a circulating liquid second-stage storage tank, a second-stage vacuum extraction circulating pump and a second-stage cooler connected in sequence; wherein each vacuum extraction unit forms a closed loop;

[0015] The inlet end of the oxygen removal head is connected with the outlet end of the first-stage vacuum pumping circulation pump and the second-stage vacuum pumping circulation pump respectively, and the intermediate connection between the oxygen removal head and the first-stage and second-stage circulation liquid storage tanks is respectively provided with a first-stage circulation liquid level control valve and a second-stage circulation liquid level control valve;

[0016] The working condition of the first-stage circulation liquid level control valve is that when the liquid level of the first-stage circulation liquid storage tank is higher than 60%, the first-stage circulation liquid level control valve is automatically opened to supplement the circulation liquid into the oxygen removal head through the first-stage vacuum pumping circulation pump.

[0017] When the liquid level is lower than 50%, the first-stage circulation liquid level control valve is automatically closed.

[0018] The liquid level control of the second-stage circulation liquid storage tank is the same as that of the first-stage circulation liquid storage tank.

[0019] The beneficial effects of the above further technical solutions are that: the present application adopts a two-stage vacuum pumping unit in series to pump the deaerator to a high vacuum state, thereby changing the partial pressure of the desalted water, removing oxygen in the desalted water at room temperature, and avoiding the problems of high energy consumption and large water vapor loss caused by steam deaeration in the prior art. The two-stage vacuum pumping unit in series can maintain a vacuum degree of-99.5 kPa or higher. The cooler connected after the first-stage vacuum pumping circulation pump is used to reduce the temperature of the circulation liquid. The high temperature of the circulation liquid is caused by the heat generated during the work of the pump and the ejector in the circulation process. If the circulation liquid enters the equipment at a negative pressure state through the nozzle, it will reach the boiling point and vaporize, which will destroy the vacuum degree. Therefore, the cooler is provided to ensure stable and normal operation of the circulation liquid at room temperature.

[0020] Further, the first-stage ejector and the second-stage ejector are a first-stage Venturi vacuumizer and a second-stage Venturi vacuumizer respectively.

[0021] Further, the first-stage and second-stage circulation liquid storage tanks are respectively provided with a first-stage demister and a second-stage demister at the top, which can prevent gas mist from being entrained.

[0022] The outlet end of the first-stage demister is connected with the inlet end of the second-stage ejector, so that the first-stage vacuum pumping unit and the second-stage vacuum pumping unit are connected in series.

[0023] Further, the outlet end of the oxygen removal head is connected with the inlet end of the first-stage ejector.

[0024] The bottom outlet end of the deaerator is connected with the inlet end of the first-stage circulation liquid storage tank.

[0025] Further, a circulating liquid level control valve is arranged between the deaerator and the primary circulating liquid storage tank.

[0026] Further, the working condition of the circulating liquid level control valve is that when the liquid level of the primary circulating liquid storage tank is higher than 60%, the circulating liquid level control valve is automatically closed, and when the liquid level is lower than 50%, the circulating liquid level control valve is automatically opened to supplement water.

[0027] The beneficial effect of the above further technical solution is that the circulating liquid level control valve is arranged between the deaerator and the primary circulating liquid storage tank, and is used in combination with the primary circulating liquid level control valve arranged between the deaerator head and the primary vacuum circulating pump, so as to ensure that the liquid level of the primary circulating liquid storage tank is at an intermediate level, avoid the problem of low liquid level causing the primary vacuum circulating pump to be empty, and enable sufficient liquid to circulate to ensure that the liquid evacuator works.

[0028] Further, the deaerator is higher than the primary circulating liquid storage tank by more than 2m, so as to ensure that the deaerated water flows smoothly from the deaerator to the primary circulating liquid storage tank under normal operation.

[0029] Further, the primary ejector includes at least three parallel ejectors.

[0030] And a valve is arranged at the inlet and outlet of each ejector.

[0031] Further, the load of the primary ejector includes at least 30%, 50%, and 70%.

[0032] The beneficial effect of the above further technical solution is that the adjustment of the suction load is determined by the load of the top nozzle of the primary circulating liquid storage tank, each liquid ejector works differently, and a valve is arranged at the inlet and outlet of each ejector, so that the high vacuum of the deaerator can be adjusted by using a single nozzle or a combination of multiple nozzles according to the load. Specifically, the sizes of the nozzles of the primary ejector are different, and the amount of circulating liquid passing through the nozzles is different, so the suction force is also different. Only in this way can the load be freely adjusted under different load conditions of the deaerator to ensure the stability of the high vacuum degree of the deaerator under different loads. If only one ejector is arranged, the adjustment space is small, and the vacuum degree cannot be adjusted when the vacuum degree is low. Only the energy consumption can be sacrificed to increase the temperature of the desalted water to compensate for the loss of the reduced vacuum degree.

[0033] Further, a system pipe network is arranged at the outer top of the secondary circulating liquid storage tank to provide desalted water for supplementing the secondary circulating liquid storage tank.

[0034] The top of the secondary defoamer is also connected with a discharge pipe.

[0035] The height of the discharge pipe from the ground is greater than 4.5m.

[0036] Further, the oxygen removal head is internally provided with a filler.

[0037] Still further, the filler is a 316L material plus regular hole plate corrugated filler or a type 452y plus hole plate corrugated filler.

[0038] The beneficial effects of the above further technical solutions are that the filler defined in the application has the advantages of high flux and low pressure drop in performance compared with ordinary conventional stainless steel hole plate corrugated fillers, which can ensure uniform distribution of gas and liquid phases and facilitate effective oxygen removal of the desalted water.

[0039] Further, the N2 stripping distributor is connected with the N2 stripping oxygen removal through a pipeline, and a nitrogen control valve is further arranged on the pipeline to strip out the removed oxygen.

[0040] Still further, the N2 stripping distributor is in the shape of a dendritic shape.

[0041] Further, the system further comprises a steam generating drum for collecting the oxygen-removed water.

[0042] The working principle of the negative pressure deoxidizing system defined in the application is as follows: the desalted water is preheated to 45 DEG C by a heating system, then enters a deoxidizing head with distributed packing inside, and then enters a deoxidizer, the deoxidizer forms a high vacuum state under the action of two-stage series vacuum pumping, so as to change the partial pressure of the desalted water, thereby achieving the purpose of deoxidizing the low-temperature desalted water, and the dissolved oxygen and other gases such as CO removed from the water are stripped out through a nitrogen stripping distributor arranged at the bottom of the deoxidizer. In the two-stage series vacuum pumping unit, the opening of the primary vacuum circulating pump must be carried out under the normal operation state of the secondary vacuum circulating pump and the secondary ejector; in the primary vacuum pumping unit: a circulating liquid level control valve is arranged in the connection between the primary circulating liquid storage tank and the deoxidizer, so as to supplement the water level in the primary circulating liquid storage tank, the interlocking logic of the circulating liquid level control valve is that the valve is automatically closed when the liquid level in the primary circulating liquid storage tank is higher than 60% of the circulating liquid level, and the valve is automatically opened to supplement water when the liquid level is lower than 50% of the circulating liquid level, because the pressures in the two tanks are different, the deoxidizer is arranged to be higher than the primary circulating liquid storage tank by more than 2 meters, so that the deoxidized water can flow smoothly into the primary circulating liquid storage tank; an air extraction line is arranged at the top of the deoxidizing head, the air extraction line is connected with the primary ejector (a Venturi air extractor), the ejector can be combined or used alone at 30%, 50% and 70% loads, the air extraction load is adjusted to control the vacuum degree, three groups of Venturi air extractors connected in parallel in the primary ejector are connected with the primary circulating liquid storage tank, a primary vacuum circulating pump is arranged at the bottom of the storage tank, a plate cooler is arranged behind the primary vacuum circulating pump, the temperature of the deoxidized water in the tank is cooled to 25 DEG C and returned to the ejector, the high-speed liquid flow can suck the gas into the primary circulating liquid storage tank, a primary circulating liquid level control valve is arranged at the other branch of the outlet side of the primary vacuum circulating pump, the liquid level is maintained stable under normal operation, the primary circulating liquid level control valve is automatically opened when the liquid level in the primary circulating liquid storage tank is higher than 60%, the deoxidized water is sent to the deoxidizer through the primary vacuum circulating pump and the deoxidizing head, the primary circulating liquid level control valve is automatically closed when the liquid level is lower than 50%; a demister is arranged at the top of the primary circulating liquid storage tank to prevent gas mist from being entrained, the gas phase at the top thereof enters the secondary ejector (a Venturi air extractor) through a pipeline, the secondary circulating liquid storage tank has the same effect as the primary circulating liquid storage tank, and is also provided with a plate cooler and a vacuum circulating pump, the outlet end of the vacuum circulating pump is connected with the deoxidizing head, and a secondary circulating liquid level control valve is arranged in the middle, so as to maintain the liquid level of the storage tank stable, a desalted water automatic water supplement control valve is arranged at the upper portion of the secondary circulating liquid storage tank, the desalted water comes from the system pipe network to maintain the liquid level stable, and a demister is arranged at the top of the secondary circulating liquid storage tank, so that the secondary circulating liquid storage tank works at normal temperature and a large amount of non-condensed water vapor is not generated.

[0043] In order to achieve the above purpose, the application further provides another technical scheme:

[0044] The negative pressure deoxidizing process specifically comprises the following steps:

[0045] (1) According to the negative pressure deoxidizing system described above, the system is first watered: the desalted water is preheated to 45 DEG C, and then watered from the deaerator, the circulating liquid first-stage liquid storage tank and the circulating liquid second-stage liquid storage tank in sequence, and after the watering in the equipment and pipelines is completed, the liquid level in the deaerator, the circulating liquid first-stage liquid storage tank and the circulating liquid second-stage liquid storage tank is kept at 50-60%;

[0046] (2) The second-stage vacuum pumping unit is started: the circulating liquid in the circulating liquid second-stage liquid storage tank is cooled to 25 DEG C by the second-stage cooler and then enters the second-stage ejector, so that the vacuum in the circulating liquid first-stage liquid storage tank is established, and the vacuum degree is -80 kPa;

[0047] (3) The first-stage vacuum pumping unit is started: under the condition that the second-stage vacuum pumping unit is stably operated, the first-stage vacuum circulating pump is started, in order to prevent the equipment from being damaged due to excessive suction force, the first-stage ejector with a load of 30% is first started, the circulating liquid in the circulating liquid first-stage liquid storage tank is cooled to 25 DEG C by the first-stage cooler and then enters the first-stage ejector with a load of 30%, so that the negative pressure in the deaerator is established, and after the negative pressure is stabilized, the first-stage ejectors with loads of 50% and 70% are gradually started, until the vacuum degree is stably above -99.5 kPa, which is normal;

[0048] (4) N2 stripping deoxidation: after the vacuum of the deaerator is normal, the nitrogen control valve is opened, and N2 stripping is used to rapidly deoxidize; the frequency of testing of deoxidizing water is increased, and after the dissolved oxygen and other gas indexes such as CO are qualified, the deoxidizing water is delivered to each steam drum.

[0049] Further, in step (1):

[0050] When the liquid level in the circulating liquid first-stage liquid storage tank is higher than 60%, the circulating liquid liquid level control valve arranged between the first-stage vacuum circulating pump and the deaerator is automatically opened, and the circulating liquid is automatically supplemented into the deaerator through the first-stage vacuum circulating pump and the deaerator head;

[0051] When the liquid level is lower than 50%, the circulating liquid liquid level control valve is automatically closed;

[0052] The liquid level control of the circulating liquid second-stage liquid storage tank is the same as that of the circulating liquid first-stage liquid storage tank.

[0053] According to the technical solution, compared with the prior art, the negative pressure deoxidizing system and process provided by the present application have the following beneficial effects:

[0054] (1) The problem of high unqualified rate of dissolved oxygen in the thermal type deaerator in the prior art is solved. On the one hand, the high vacuum degree of the deaerator is realized by using liquid vacuum pumping series operation to change the partial pressure of the softened water; on the other hand, the dissolved oxygen and other gases such as CO are separated and rapidly removed by nitrogen stripping, so that the deoxidizing rate is improved.

[0055] (2)Saving steam consumption reduces operating energy consumption. The existing thermal deaerator injects steam at the lower part of the deaeration head filler layer; and the present application adopts vacuum deaeration at room temperature to avoid the problem of high energy consumption caused by steam.

[0056] (3)No water vapor loss caused by exhaust steam. The thermal deaerator will produce a large amount of exhaust steam to the atmosphere due to the injection of steam to warm the softened water, resulting in serious water vapor loss; and the present application is provided with a demister at the upper exhaust port of the circulating liquid secondary storage tank, which works at room temperature and will not produce a large amount of non-condensable water vapor. BRIEF DESCRIPTION OF DRAWINGS

[0057] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings described below are only a part of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0058] Figure 1 The accompanying drawings provide a structure schematic diagram of a negative pressure deaeration system. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0060] Embodiment 1

[0061] A negative pressure deaeration system, comprising a heating system, a deaeration system and a vacuum pumping system connected in sequence;

[0062] The heating system comprises a heating furnace.

[0063] The deaeration system comprises a deaerator, a deaeration head and an N2 stripping distributor.

[0064] The deaeration head is arranged at the outer top of the deaerator.

[0065] The N2 stripping distributor is arranged at the bottom of the inner cavity of the deaerator, connected with the N2 stripping deaeration pipeline, and further provided with a nitrogen control valve in the middle to strip out the removed oxygen; wherein the N2 stripping distributor is in the shape of a branch.

[0066] The vacuum pumping system comprises a primary vacuum pumping unit and a secondary vacuum pumping unit connected in series.

[0067] The primary vacuum unit comprises a primary ejector, a primary circulating liquid storage tank, a primary vacuum circulating pump and a primary cooler connected in sequence;

[0068] The secondary vacuum unit comprises a secondary ejector, a secondary circulating liquid storage tank, a secondary vacuum circulating pump and a secondary cooler connected in sequence; wherein the ejector is a Venturi vacuumizer;

[0069] The primary circulating liquid storage tank and the secondary circulating liquid storage tank are respectively provided with a primary demister and a secondary demister at the top;

[0070] The outlet end of the primary demister is connected with the inlet end of the secondary ejector, so that the primary vacuum unit and the secondary vacuum unit are connected in series;

[0071] The outlet end of the deaerating head is connected with the inlet end of the primary ejector; the inlet end of the deaerating head is respectively connected with the outlet end of the primary vacuum circulating pump and the secondary vacuum circulating pump, and a primary circulating liquid level control valve and a secondary circulating liquid level control valve are respectively arranged in the middle; when the liquid level of the primary circulating liquid storage tank is higher than 60%, the primary circulating liquid level control valve is automatically opened to supplement the circulating liquid into the deaerator through the primary vacuum circulating pump and the deaerating head; when the liquid level is lower than 50%, the primary circulating liquid level control valve is automatically closed; wherein the secondary circulating liquid level control valve has the same effect as the primary circulating liquid level control valve, and can automatically maintain the liquid level of the secondary circulating liquid storage tank stable; in addition, the outlet end of the deaerator is connected with the inlet end of the primary circulating liquid storage tank, and a circulating liquid level control valve is arranged in the middle of the connection between the deaerator and the primary circulating liquid storage tank; the working condition is that the circulating liquid level control valve is automatically closed when the liquid level is higher than 60% and is automatically opened when the liquid level is lower than 50% to supplement water, so as to ensure that the liquid level of the primary circulating liquid storage tank is at the middle level, avoid the problem of low liquid level causing the primary vacuum circulating pump to be difficult to pump, and enable sufficient liquid to circulate to ensure that the liquid vacuumizer works.

[0072] In order to optimize the technical scheme, the deaerator is higher than the primary circulating liquid storage tank by more than 2m, so that the deaerated water can flow smoothly from the deaerator into the primary circulating liquid storage tank under normal operation.

[0073] In order to optimize the technical scheme, the primary ejector comprises at least three parallel ejectors; and a valve is arranged at the inlet and outlet of each ejector. The load of the primary ejector is adjusted, each ejector works differently, and a valve is arranged at the inlet and outlet of each ejector, so that a single nozzle or multiple nozzles can be used according to the load to adjust the vacuum degree in the deaerator.

[0074] Further optimization of the technical scheme, the load of the primary ejector at least includes 30%, 50% and 70%.

[0075] In order to optimize the technical scheme, the outer top of the secondary circulating liquid storage tank is provided with a system pipe network to provide desalted water for the secondary circulating liquid storage tank.

[0076] The top of the secondary defoaming device is also connected with a discharge pipe.

[0077] The height of the discharge pipe opening from the ground is greater than 4.5 m.

[0078] In order to optimize the technical scheme, the inside of the deaerating head is provided with fillers, and 316L material plus regular hole plate corrugated fillers or model 452y plus hole plate corrugated fillers are selected, so that they have the advantages of high flux and low pressure drop.

[0079] In order to optimize the above technical scheme, the system further comprises a steam drum connected with the deaerator for collecting deaerated water. One of the negative pressure deaerating system structural diagrams is shown in Figure 1 The water boiling point and the vacuum degree are shown in Table 1.

[0080] Table of water boiling point and vacuum degree

[0081] Temperature (°C) Vacuum (kPa) Temperature (°C) Vacuum (kPa) Temperature (°C) Vacuum (kPa) Temperature (°C) Vacuum (kPa) Temperature (°C) Vacuum (kPa) 0 -100.5 20 -98.7 40 -93.7 60 -81.2 80 -53.9 1 -100.4 21 -98.6 41 -93.3 61 -80.3 81 -51.9 2 -100.4 22 -98.4 42 -92.9 62 -79.3 82 -49.9 3 -100.j 23 -98.3 43 -92.5 63 -78.3 83 -47.8 4 -100.3 24 -98.1 44 -92.0 64 -77.2 84 -45.6 5 -100.2 25 -97.9 45 -91.5 65 -76.1 85 -43.4 6 -100.1 26 -97.7 46 -91.0 66 -75.0 86 -41.1 7 -100.1 27 -97.5 47 -90.5 67 -73.8 87 -38.7 8 -100.0 28 -97.3 48 -89.9 68 -72.6 88 -36.3 9 -99.9 29 -97.1 49 -89.4 69 -71.3 89 -33.8 10 -99.9 30 -96.8 50 -88.8 70 -70.0 90 -31.2 11 -99.8 31 -96.6 51 -88.2 71 -68.0 91 -28.5 12 -99.7 32 -96.3 52 -87.5 72 -67.0 91 -25.7 13 -99.6 33 -96.1 53 -86.8 73 -65.7 93 -22.8 14 -99.5 34 -958 54 -86.1 74 -64.2 94 -19.8 15 -99.4 35 -95.5 55 -85.4 75 -62.6 95 -16.8 16 -99.3 36 -95.2 56 -84.6 76 -61.0 96 -11.6 17 -99.1 37 -94.8 57 -83.8 77 -59.3 97 -10.4 18 -99.0 38 -94.5 58 -83.0 78 -57.5 98 -7.0 19 -98.9 39 -94.1 59 -82.1 79 -55.7 99 -3.6

[0082] Note: 1 standard atmospheric pressure = 1.01325*10 5 Pa = 101.325 KPa

[0083] Table 1

[0084] Example 2

[0085] Based on the negative pressure deaerating system of Example 1, this embodiment discloses a negative pressure deaerating process. The process conditions before starting are confirmed: the equipment and facility test is completed, the system is supplemented with desalted water and the test is qualified, the automatic control valve debugging is normal, the pump test operation is normal, each equipment is put into use, and the process system flow is confirmed to be changed and confirmed to be completed. The specific process steps are:

[0086] (1) System water supply: desalted water is preheated to 45℃ by a heating furnace flue, and then starts to be sequentially supplemented from the deaerator, the circulating liquid primary storage tank and the circulating liquid secondary storage tank, and the water supply in the equipment and pipeline is completed, and the liquid level in the deaerator, the circulating liquid primary storage tank and the circulating liquid secondary storage tank is maintained at 50-60%; wherein, the water amount of the desalted water entering the deaerator is automatically supplemented according to the steam production of each steam drum.

[0087] (2) Start the secondary Venturi air extractor, form a vacuum state in the circulating liquid primary storage tank, start the secondary vacuum circulating pump, and the circulating liquid cooled to 25℃ by the primary plate cooler enters the secondary Venturi air extractor, to establish a vacuum in the circulating liquid primary storage tank, and the vacuum degree is about -80 kPa, and the primary Venturi air extractor is started under stable state.

[0088] (3) Start the first stage Venturi vacuum pump, to prevent the equipment suction caused by excessive damage to the equipment, first in the case of opening the first stage vacuum circulating pump, open 30% load before and after the first stage Venturi vacuum pump valve, through the second plate cooler to 25 DEG C circulating liquid into the first stage Venturi vacuum pump, slowly establish a negative pressure in the deaerator, after the negative pressure value is stable gradually open 50%, 70% to vacuum stability to-99.5 kPa above normal.

[0089] (4) deaerator vacuum normal after opening nitrogen control valve using N2 stripping rapid deoxygenation, increase the frequency of deoxygenated water test, dissolved oxygen and CO and other gas indicators qualified to each steam drum.

[0090] In order to optimize the technical scheme, when the circulating liquid level of the first stage liquid tank is higher than 60% upper limit, the first stage circulating liquid level control valve between the deaerator head and the first stage circulating liquid tank is automatically opened, the circulating liquid level control valve between the deaerator and the first stage circulating liquid tank is automatically closed, and the circulating liquid is automatically supplemented into the deaerator through the first stage vacuum circulating pump and the deaerator head.

[0091] If it is lower than 50%, the first stage circulating liquid level control valve between the deaerator head and the first stage circulating liquid tank is automatically closed; the circulating liquid level control valve between the deaerator and the first stage circulating liquid tank is opened, and the circulating liquid of the first stage circulating liquid tank is supplemented.

[0092] And the circulating liquid level control condition of the second stage circulating liquid tank is:

[0093] When the circulating liquid level of the second stage circulating liquid tank is higher than 60% upper limit, the second stage circulating liquid level control valve between the deaerator head and the second stage circulating liquid tank is automatically opened, and the circulating liquid is automatically supplemented into the deaerator through the second stage vacuum circulating pump and the deaerator head.

[0094] If it is lower than 50%, the second stage circulating liquid level control valve between the deaerator head and the second stage circulating liquid tank is automatically closed; the circulating liquid of the second stage circulating liquid tank is supplemented through the system pipe network arranged at the top of the second stage circulating liquid tank.

[0095] Effect verification

[0096] The technical effect of the present application is mainly evaluated by the deoxygenation qualified rate. According to GB / T12145-2016, the dissolved oxygen index of the feedwater of the high-pressure boiler (3.8-5.8 MPa) is ≤15 ug / L, and the deoxygenation qualified rate is defined as: the number of times that the feedwater dissolved oxygen is ≤15 ug / L in a period of time divided by the total number of dissolved oxygen analysis times.

[0097] Among them, the comparison of the vacuum deoxygenation and the thermal deoxygenation of the present application is shown in Tables 2 and 3.

[0098]

[0099] Table 2

[0100] Note: In the table, the value "+" means saving amount, benefit increase; the value "-" means consumption increase amount, benefit decrease. The annual running time is 8400 hours.

[0101]

[0102] Table 3

[0103] In summary, before the application is put into use, the deoxygenation qualified rate is about 80%, after the application is used, the deoxygenation qualified rate reaches more than 99%, the deoxygenation limit can reach below 1 ug / L and continuously and stably operates, the boiler feed water quality is greatly improved, the vacuum deoxygenation compared with the thermal deoxygenation can save energy more than 90%. Taking the 130t / h steam thermal deoxygenation boiler which is reformed by using the vacuum deoxygenation technology as an example, about 54600 tons of deoxygenation steam of deoxygenator is saved per year (according to the annual running time of 8400 hours), after deducting the increased consumption of electricity and nitrogen gas (99.99% purity), the direct economic benefit of 1092 million yuan per year is generated.

[0104] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0105] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A negative pressure deoxygenation system, characterized in that, It includes a heating system, a deoxygenation system, and a vacuum system connected in sequence; The deoxygenation system includes: a deaerator, a deaerator head, and an N2 stripping distributor; The heating system is connected to the deaerator head; The deaerator head is fixed to the top of the deaerator; The N2 stripping distributor is located at the bottom of the deaerator's inner cavity; The vacuum system includes: a primary vacuum unit and a secondary vacuum unit; in, The primary vacuum unit includes: a primary ejector, a primary circulating liquid storage tank, a primary vacuum circulation pump, and a primary cooler connected in sequence. The secondary vacuum unit includes: a secondary ejector, a secondary circulating liquid storage tank, a secondary vacuum circulation pump, and a secondary cooler connected in sequence from end to end; The inlet end of the deoxygenation head is connected to the outlet ends of the first-stage vacuum circulation pump and the second-stage vacuum circulation pump, respectively, and a first-stage circulating liquid level control valve and a second-stage circulating liquid level control valve are respectively provided in the middle of the connection between the deoxygenation head and the first-stage circulating liquid storage tank and the second-stage circulating liquid storage tank. The outlet end of the deaerator head is connected to the inlet end of the first-stage injector; The outlet end of the deaerator is connected to the inlet end of the primary circulating liquid storage tank; A circulating liquid level control valve is also installed between the deaerator and the primary circulating liquid storage tank.

2. The negative pressure deoxygenation system according to claim 1, characterized in that, A primary demister and a secondary demister are respectively installed on the top of the primary circulating liquid storage tank and the secondary circulating liquid storage tank; The outlet end of the primary demister is connected to the inlet end of the secondary ejector.

3. The negative pressure deoxygenation system according to claim 1, characterized in that, The first-stage injector includes at least three injectors connected in parallel; Furthermore, each injector is equipped with a valve at its inlet and outlet.

4. The negative pressure deoxygenation system according to claim 3, characterized in that, The load on the first-stage injector includes at least 30%, 50%, and 70%.

5. A negative pressure deoxygenation system according to claim 1, characterized in that, The N2 stripping distributor is connected to the N2 stripping deoxygenation pipeline.

6. The negative pressure deoxygenation system according to claim 1, characterized in that, The system also includes a steam generator connected to the deaerator for collecting qualified deoxygenated water.

7. A negative pressure deoxygenation process, characterized in that, Specifically, the following steps are included: (1) A negative pressure deoxygenation system according to any one of claims 1-6, wherein the system is first replenished with water: the demineralized water is preheated to 45°C and then replenished with water sequentially from the deoxygenator, the primary storage tank of the circulating liquid, and the secondary storage tank of the circulating liquid; The liquid levels in the deaerator, the primary circulating liquid storage tank, and the secondary circulating liquid storage tank are maintained at 50-60%. (2) Start the secondary vacuum unit: Start the secondary vacuum circulation pump. The circulating liquid in the secondary storage tank is cooled to 25°C by the secondary cooler and then enters the secondary ejector to establish a vacuum in the primary storage tank of the circulating liquid. (3) Start the first-stage vacuum pumping unit: Under the stable operation of the second-stage vacuum pumping unit, start the first-stage vacuum pumping circulation pump, and then start the first-stage ejector with a load of 30%. The circulating liquid in the first-stage storage tank is cooled to 25°C by the first-stage cooler and then enters the first-stage ejector with a load of 30%, thereby establishing negative pressure in the deaerator. After the negative pressure stabilizes, the first-stage ejectors with loads of 50% and 70% are gradually started. (4) N2 stripping deoxygenation: After the deaerator is in normal vacuum, N2 stripping is used for rapid deoxygenation; after the deoxygenation is qualified, the deoxygenated water is transported to the steam drum.

8. The negative pressure deoxygenation process according to claim 7, characterized in that, In step (1): If the liquid level in the primary storage tank of the circulating liquid is higher than 60%, the primary circulating liquid level control valve set between the primary vacuum circulation pump and the deoxygenation head will automatically open, and the circulating liquid will be automatically replenished into the deoxygenation head through the primary vacuum circulation pump. If the level is below 50%, the primary circulating liquid level control valve will automatically close. The liquid level control of the secondary storage tank of the circulating liquid is the same as that of the primary storage tank of the circulating liquid.

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