Zero-steam-consumption waste heat utilization system for boiler feed water

Abstract

Provided in the present invention is a zero-steam-consumption waste heat utilization system for boiler feed water. The system comprises: a vacuum-stripping deaeration unit, which comprises a plurality of vacuum strippers combined in series and parallel; a multi-stream heat exchanger, a first heat-exchange section and a second heat-exchange section of which have deaerated water pipelines in communication with each other and heat source pipelines independent of each other; a working medium heat exchanger, wherein a water outlet of the vacuum-stripping deaeration unit is connected to a deaerated water output port via the deaerated water pipelines of the multi-stream heat exchanger and a deaerated water pipe of the working medium heat exchanger in sequence; and a working medium evaporator, wherein a heat source pipe of the working medium evaporator has one end connected to a heat source water inlet and the other end connected to a heat source water return port via the heat source pipeline of the first heat-exchange section, the heat source water inlet is further connected to the heat source water return port via the heat source pipeline of the second heat-exchange section, and a second working medium pipeline of the working medium evaporator and a first working medium pipeline of the working medium heat exchanger forming a cycle. The present invention can ensure that the dissolved oxygen indicator of deaerated water is standard-compliant, reduce operation energy consumption, ensure that the temperature indicator of the deaerated water is standard-compliant, and finally produce standard-compliant boiler feed water.

Description

Zero steam consumption boiler feedwater waste heat utilization system Technical Field

[0001] This invention relates to the field of energy conservation and environmental protection technology, and more specifically, to a zero-steam-consumption boiler feedwater waste heat utilization system. Background Technology

[0002] In industry, deoxygenated water is the feed water source for boiler steam production. According to steam production process requirements, the dissolved oxygen level of deoxygenated water must meet the specifications of 5 μg / L to 100 μg / L, and the temperature must meet the specifications of 104℃ to 156℃. If the dissolved oxygen exceeds the standard, oxygen corrosion will accelerate equipment corrosion at temperatures above 100℃, posing a significant threat to the safe operation of steam production. To meet the oxygen content requirements of boiler feedwater, commonly used deoxygenation methods in existing technologies include: thermal deoxygenation, vacuum deoxygenation, degassing membrane deoxygenation, redox resin deoxygenation, and sodium sulfite deoxygenation.

[0003] Among these technologies, thermal deoxygenation meets the deoxygenation index requirements, but the deoxygenation process consumes a large amount of steam, resulting in high energy consumption and operating costs, high carbon emissions, and uneconomical operation. Vacuum deoxygenation and degassing membrane deoxygenation technologies meet the deoxygenation index requirements and have low operating energy consumption, but the temperature of the deoxygenated water produced is close to room temperature (20℃ to 40℃), and subsequent steam generation requires the consumption of waste heat or steam for heating. From a system perspective, this does not reduce energy consumption and operating costs. If a combination of degassing membrane and waste heat utilization is used, producing deoxygenated water at 104℃ to 156℃ requires the waste heat side to reach above 110℃ to 160℃, which greatly limits the application range of this technology. Oxidation-reduction resin deoxygenation and sodium sulfite deoxygenation have unstable deoxygenation indexes and require steam heating. In addition, the dosage of added chemicals is relatively large, resulting in high operating costs and relatively limited application.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a zero-steam-consumption boiler feedwater waste heat utilization system to solve the problems existing in the current deoxygenation technology, which can ensure that the dissolved oxygen index of the deoxygenated water is qualified, reduce the operating energy consumption cost, and ensure that the temperature index of the deoxygenated water is qualified, and finally produce qualified boiler feedwater.

[0006] According to one aspect of the present invention, a zero-steam-consumption boiler feedwater waste heat utilization system is provided, comprising: a vacuum lifting deaerator unit connected to a demineralized water inlet, the vacuum lifting deaerator unit comprising a plurality of vacuum lifters connected in series, wherein the series nodes of adjacent vacuum lifters are also connected to the demineralized water inlet via a main inlet pipeline; a multi-stream heat exchanger comprising a first heat exchange section and a second heat exchange section respectively including a deaerated water pipeline and a heat source pipeline, the first heat exchange section and the second heat exchange section being connected to the deaerated water pipeline, and the heat source pipelines being independent; and a working fluid heat exchanger comprising a deaerated water pipeline. The vacuum lifting deoxygenation unit's outlet is connected to the deoxygenated water outlet via the deoxygenated water pipeline of the first heat exchange section, the deoxygenated water pipeline of the second heat exchange section, and the deoxygenated water pipeline. The working fluid evaporator includes a heat source pipeline and a second working fluid pipeline. One end of the heat source pipeline is connected to the heat source inlet, and the other end is connected to the heat source return outlet via the heat source pipeline of the first heat exchange section. The heat source inlet is also connected to the heat source return outlet via the heat source pipeline of the second heat exchange section. The second working fluid pipeline and the first working fluid pipeline form a working fluid circulation pipeline.

[0007] In some embodiments, each of the vacuum lifters has an inlet and an outlet, wherein the outlet of the preceding vacuum lifter is connected in series with the inlet of the following vacuum lifter, and the series connection node between the inlet of the first vacuum lifter and the outlet of the preceding vacuum lifter and the inlet of the following vacuum lifter is connected to the demineralized water inlet via the main water inlet pipeline.

[0008] In some embodiments, each of the vacuum lifters further has an air inlet and an air outlet, with the air inlet of each vacuum lifter connected to an inert gas inlet and the air outlet of each vacuum lifter connected to a vacuum pump.

[0009] In some embodiments, the inert gas is nitrogen, and the purity of the nitrogen is greater than or equal to 99.9%.

[0010] In some embodiments, the zero-steam-consumption boiler feedwater waste heat utilization system further includes a filter connected between the demineralized water inlet and the vacuum lift deoxygenation unit.

[0011] In some embodiments, the zero-steam-consumption boiler feedwater waste heat utilization system further includes: a compressor connected in a pipeline from the second working fluid pipeline to the first working fluid pipeline; and a throttling expansion valve connected in a pipeline from the first working fluid pipeline to the second working fluid pipeline.

[0012] In some embodiments, the zero-steam-consumption boiler feedwater waste heat utilization system further includes: a booster pump connected between the deoxygenated water pipeline and the deoxygenated water outlet.

[0013] In some embodiments, the working fluid flowing in the working fluid circulation pipeline is a non-azeotropic working fluid, which comprises the following components: 5% to 35% by mass of trans-1,3,3,3-tetrafluoropropylene, 10% to 15% by mass of pentafluoropropane, and 50% to 85% by mass of trans-1-chloro-3,3,3-trifluoropropylene.

[0014] In some embodiments, the temperature of the demineralized water entering the demineralized water inlet is 20°C to 40°C and the pressure is 0.3 MPag to 1.0 MPag; the temperature of the heat transfer water entering the heat source inlet is 70°C to 95°C, and the temperature of the heat transfer water flowing out of the heat source return inlet is 50°C to 80°C.

[0015] In some embodiments, the temperature of the deoxygenated water flowing out of the multi-stream heat exchanger is 70°C to 90°C, and the temperature of the deoxygenated water flowing out of the deoxygenated water outlet is 104°C to 156°C, and the pressure is 0.2 MPag to 10 MPag.

[0016] The beneficial effects of this invention compared to the prior art include at least the following:

[0017] The zero-steam-consumption deoxygenation process proposed in this invention is based on vacuum lifting deoxygenation, cascade utilization of waste heat from the heat source, and upgraded utilization of waste heat from working fluid circulation. It effectively solves the problems existing in the current deoxygenation technology, and achieves zero steam consumption while ensuring that the dissolved oxygen index of the deoxygenated water meets the requirements. It fully recovers and utilizes the waste heat from the heat source, achieves significant energy-saving benefits, and ensures that the temperature index of the deoxygenated water meets the requirements. It can continuously produce deoxygenated water at 104℃ to 156℃ as boiler feedwater.

[0018] This invention first achieves room temperature deoxygenation at 20°C to 40°C using a vacuum lifting deoxygenation unit to meet deoxygenation requirements. Then, through the cascade utilization of waste heat from the heat source, the deoxygenated water is heated to 70°C to 90°C via a multi-stream heat exchanger. Next, using the working fluid circulation waste heat upgrade utilization technology, the deoxygenated water is heated to the set temperature (104°C to 156°C) via a working fluid heat exchanger. Finally, deoxygenated water of different grades is produced according to user needs. The entire process does not require steam consumption, achieving zero steam consumption deoxygenation throughout the entire process.

[0019] Among them, the vacuum lifting deoxygenation unit adopts multiple vacuum lifters in series and parallel combination. By connecting them in series, it can achieve deep removal of deoxygenation indicators, and by connecting them in parallel, it can achieve online removal, cleaning and replacement, which will not cause downtime risk to the system operation and improve the system's deoxygenation indicators and operational reliability.

[0020] Using the working fluid as a circulating medium for waste heat upgrading, and combining the characteristic of no phase change heat in the cooling process of the heat source and the heating process of the deoxygenated water, a waste heat upgrading process cycle is established. First, the waste heat from the heat source is used to gradually evaporate and exchange heat through the working fluid in an evaporator. Then, the working fluid exchanges heat with the deoxygenated water in a staged condensation process through a heat exchanger. Taking advantage of the temperature glide during the evaporation and condensation of the working fluid, a temperature-changing process is achieved by exchanging heat between the working fluid during condensation and evaporation and the deoxygenated water and the heat source. Considering the actual situation that the temperatures of the deoxygenated water and the heat source are changing, this cycle process closely matches the actual heat exchange process, thus effectively improving energy efficiency.

[0021] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0023] Figure 1 shows a schematic diagram of the zero-steam-consumption boiler feedwater waste heat utilization system in an embodiment of the present invention.

[0024] Figure 2 shows a schematic diagram of the medium flow in the zero-steam-consumption boiler feedwater waste heat utilization system in an embodiment of the present invention. Detailed Implementation

[0025] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to those described herein. Rather, these embodiments are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0026] The accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted.

[0027] In the description of this invention, the terms "first," "second," and similar words do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The term "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, in the description of this invention, when it is said that a device is "connected" to another device, this includes not only direct connections but also indirect connections via other elements.

[0028] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features in different embodiments can be combined with each other.

[0029] Figure 1 illustrates the structure of the zero-steam-consumption boiler feedwater waste heat utilization system in an embodiment of the present invention. Referring to Figure 1, the zero-steam-consumption boiler feedwater waste heat utilization system provided in this embodiment of the present invention includes:

[0030] Vacuum lifting deoxygenation unit 20 is connected to demineralized water inlet 81. Vacuum lifting deoxygenation unit 20 includes multiple vacuum lifters connected in series (e.g., including primary vacuum lifter 2A, secondary vacuum lifter 2B, tertiary vacuum lifter 2C and quaternary vacuum lifter 2D, but not limited thereto). The series nodes of adjacent vacuum lifters are also connected to demineralized water inlet 81 via the main water inlet pipeline 82.

[0031] The multi-flow heat exchanger 30 includes a first heat exchange section 3A and a second heat exchange section 3B, which respectively contain a deoxygenated water pipeline 31 and a heat source pipeline 32 (wherein, the first heat exchange section 3A is the medium-temperature section of the multi-flow heat exchanger 30, and the second heat exchange section 3B is the low-temperature section of the multi-flow heat exchanger 30). The deoxygenated water pipelines 31 of the first heat exchange section 3A and the second heat exchange section 3B are connected, while the heat source pipelines 32 are independent.

[0032] The working fluid heat exchanger 40 includes a deoxygenated water pipeline 41 and a first working fluid pipeline 42. The outlet of the vacuum lifting deoxygenation unit 20 (i.e., the outlet 22 of the four-stage vacuum lifter 2D) is connected to the deoxygenated water outlet 84 via the deoxygenated water pipeline 31 of the first heat exchange section 3A, the deoxygenated water pipeline 31 of the second heat exchange section 3B, and the deoxygenated water pipeline 41 of the working fluid heat exchanger 40.

[0033] The working fluid evaporator 50 includes a heat source pipe 51 and a second working fluid pipe 52. One end of the heat source pipe 51 of the working fluid evaporator 50 is connected to the heat source inlet 71 and the other end is connected to the heat source return inlet 72 via the heat source pipe 32 of the first heat exchange section 3A. The heat source inlet 71 is also connected to the heat source return inlet 72 via the heat source pipe 32 of the second heat exchange section 3B. The second working fluid pipe 52 of the working fluid evaporator 50 and the first working fluid pipe 42 of the working fluid heat exchanger 40 form a working fluid circulation pipe.

[0034] The zero-steam-consumption deoxygenation process proposed in this invention is based on vacuum lifting deoxygenation, cascade utilization of waste heat from the heat source, and upgraded utilization of waste heat from working fluid circulation. It effectively solves the problems existing in the current deoxygenation technology, and achieves zero steam consumption while ensuring that the dissolved oxygen index of the deoxygenated water meets the requirements. It fully recovers and utilizes the waste heat from the heat source, achieves significant energy-saving benefits, and ensures that the temperature index of the deoxygenated water meets the requirements. It can continuously produce deoxygenated water at 104℃ to 156℃ as boiler feedwater.

[0035] This invention first achieves room temperature deoxygenation at 20°C to 40°C using a vacuum deoxygenation unit 20 to meet deoxygenation requirements. Then, through the cascade utilization of waste heat from the heat source, the deoxygenated water is heated to 70°C to 90°C via a multi-stream heat exchanger 30. Next, using the working fluid circulation waste heat upgrade utilization technology, the deoxygenated water is heated to a set temperature (104°C to 156°C) via a working fluid heat exchanger 40. Finally, deoxygenated water of different grades is produced according to user needs. The entire process does not require steam consumption, achieving zero steam consumption deoxygenation throughout the process.

[0036] Among them, the vacuum lifting deoxygenation unit 20 adopts multiple vacuum lifters in series and parallel combination. By connecting them in series, it can achieve deep removal of deoxygenation indicators, and by connecting them in parallel, it can achieve online removal, cleaning and replacement, which will not cause downtime risk to the system operation and improve the system's deoxygenation indicators and operational reliability.

[0037] The working fluid, used as a circulating working fluid for waste heat upgrading, is designed based on the characteristic of no phase change heat during the cooling of the heat source and the heating of the deoxygenated water. First, the waste heat from the heat source is used to progressively evaporate and exchange heat through the working fluid evaporator 50. Then, the working fluid undergoes progressive condensation and heat exchange with the deoxygenated water through the working fluid heat exchanger 40. Utilizing the temperature glide advantage during the evaporation and condensation processes, a variable-temperature process is achieved by exchanging heat between the working fluid during condensation and evaporation and the deoxygenated water and heat source. Considering the changing temperatures of the deoxygenated water and heat source, this cycle closely resembles the actual heat exchange process, effectively improving energy efficiency.

[0038] Compared to conventional thermal deoxygenation technology, this invention can produce deoxygenated water of the same quality, while reducing costs and energy consumption by more than 60%; this invention also does not require steam consumption, achieving zero steam consumption deoxygenation throughout the entire process.

[0039] Compared to conventional deaeration membrane deoxygenation technology, this invention uses a series-parallel combination process of vacuum lifters to achieve deep removal of deoxygenation indicators and online removal, cleaning and replacement, thereby improving the system's deoxygenation indicators and operational reliability. Furthermore, this invention can produce deoxygenated water at temperatures ranging from 104°C to 156°C according to user needs, which is significantly different from the water supply indicators of conventional deaeration membrane deoxygenation technology.

[0040] Compared to conventional room-temperature deoxygenation + waste heat exchange technology, this invention effectively solves the problem of not being able to produce deoxygenated water above 100℃, or even if deoxygenated water above 100℃ is produced, the waste heat quality requirement is very high, resulting in the need for the waste heat side to reach above 110℃ to 160℃ if deoxygenated water at 104℃ to 156℃ is required. This invention does not have high requirements for waste heat quality and can use conventional heat transfer medium water as a heat source. Through a stepped heat exchange + waste heat upgrading utilization method, the deoxygenated water is gradually heated to the set temperature. This not only meets the user's quality requirements for deoxygenated water, but also has low requirements for waste heat quality, greatly expanding the application range.

[0041] In some embodiments, each vacuum lifter has an inlet and an outlet, wherein the outlet of the preceding vacuum lifter is connected in series with the inlet of the following vacuum lifter (i.e., the outlet 22 of the first-stage vacuum lifter 2A is connected in series with the inlet 21 of the second-stage vacuum lifter 2B, the outlet 22 of the second-stage vacuum lifter 2B is connected in series with the inlet 21 of the third-stage vacuum lifter 2C, and the outlet 22 of the third-stage vacuum lifter 2C is connected in series with the inlet 21 of the fourth-stage vacuum lifter 2D), and the first The inlet of each vacuum lifter (i.e., the inlet 21 of the first-stage vacuum lifter 2A) and the series connection nodes between the outlet of the previous vacuum lifter and the inlet of the next vacuum lifter (including the series connection node between the first-stage vacuum lifter 2A and the second-stage vacuum lifter 2B, the series connection node between the second-stage vacuum lifter 2B and the third-stage vacuum lifter 2C, and the series connection node between the third-stage vacuum lifter 2C and the fourth-stage vacuum lifter 2D) are connected to the demineralized water inlet 81 via the main water inlet pipeline 82.

[0042] In some embodiments, each vacuum lifter also has an inlet and an outlet, with the inlet of each vacuum lifter connected to an inert gas inlet 91 and the outlet of each vacuum lifter connected to a vacuum pump 92.

[0043] The vacuum lifter is equipped with polymer internal components that allow only oxygen molecules dissolved in the demineralized water to pass through. In addition, under the negative pressure of the vacuum pump 92 and the action of inert gas, dissolved oxygen in the demineralized water is continuously and stepwise removed through multiple vacuum lifters, finally meeting the requirements for deoxygenated water (usually designed to be no higher than 7 ppb).

[0044] In some embodiments, the inert gas is nitrogen, and the purity of the nitrogen is greater than or equal to 99.9%. By designing the nitrogen purity to be greater than or equal to 99.9% (mol%), the deoxygenation effect of the demineralized water is ensured.

[0045] In some embodiments, the zero-steam-consumption boiler feedwater waste heat recovery system further includes a filter 10 connected between the demineralized water inlet 81 and the vacuum lift deoxygenation unit 20. The filter 10 is used to deeply remove solid particles and bacteria from the demineralized water.

[0046] In some embodiments, the zero-steam-consumption boiler feedwater waste heat utilization system further includes: a compressor 60 connected in a pipe from the second working fluid line 52 of the working fluid evaporator 50 to the first working fluid line 42 of the working fluid heat exchanger 40; and a throttling expansion valve K connected in a pipe from the first working fluid line 42 of the working fluid heat exchanger 40 to the second working fluid line 52 of the working fluid evaporator 50.

[0047] The working fluid circulation pipeline, which connects the second working fluid pipeline 52 of the working fluid evaporator 50 to the compressor 60, the first working fluid pipeline 42 of the working fluid heat exchanger 40, the throttling expansion valve K, and the second working fluid pipeline 52 of the working fluid evaporator 50, forms a circulating working fluid for waste heat upgrading and utilization. Combining the characteristics of no phase change heat in the cooling process of the heat source and the heating process of the deoxygenated water, a waste heat upgrading and utilization process cycle is established. First, utilizing the waste heat from the heat source, the working fluid is gradually evaporated and heat exchanged through the working fluid evaporator 50. Then, the working fluid is pressurized to a set pressure by the compressor 60, and then gradually condensed and heat-exchanged with the deoxygenated water through the working fluid heat exchanger 40. Finally, the cycle is completed through the throttling expansion valve K. This process is close to the ideal Lorentz cycle. Compared with the near-isothermal process of condensation and evaporation in the conventional reverse Carnot cycle, this invention utilizes the temperature glide advantage of the working fluid evaporation and condensation process to achieve a variable temperature process by exchanging heat between the working fluid condensation and evaporation and the deoxygenated water and the heat source. Considering the actual situation that the temperatures of the deoxygenated water and the heat source are changing, the cycle process of this invention is more in line with the actual heat exchange process, which effectively improves energy efficiency and reduces costs and energy consumption by more than 25%.

[0048] In some embodiments, the zero-steam-consumption boiler feedwater waste heat utilization system further includes: a booster pump 44 connected between the deoxygenated water pipeline 41 and the deoxygenated water outlet 84 of the working fluid heat exchanger 40, to help output qualified deoxygenated water for boiler use.

[0049] Figure 2 illustrates the medium flow in the zero-steam-consumption boiler feedwater waste heat utilization system in this embodiment of the invention. The process flow for generating qualified boiler water using the zero-steam-consumption boiler feedwater waste heat utilization system will be described below with reference to Figures 1 and 2.

[0050] The demineralized water S-1 comes from upstream and first enters filter 10 to deeply remove solid particles and bacteria from the demineralized water. The filtered demineralized water S-2 enters the vacuum lift deoxygenation unit 20 for deoxygenation; among them, the demineralized water S-3 entering the first-stage vacuum lifter 2A, the demineralized water S-4 entering the second-stage vacuum lifter 2B, the demineralized water S-5 entering the third-stage vacuum lifter 2C, and the demineralized water S-6 entering the fourth-stage vacuum lifter 2D can come from the previous vacuum lifter and / or from the filtered demineralized water S-2. In addition, the nitrogen S-8 entering the system is split into several parts: nitrogen S-8A enters the first-stage vacuum lifter 2A (when the first-stage vacuum lifter 2A is in operation), nitrogen S-8B enters the second-stage vacuum lifter 2B (when the second-stage vacuum lifter 2B is in operation), nitrogen S-8C enters the third-stage vacuum lifter 2C (when the third-stage vacuum lifter 2C is in operation), and nitrogen S-8D enters the fourth-stage vacuum lifter 2D (when the fourth-stage vacuum lifter 2D is in operation). The vacuum lifters are equipped with special polymer internal components that allow only oxygen molecules dissolved in the demineralized water to pass through. Under the negative pressure of the vacuum pump 92 and the action of nitrogen, dissolved oxygen in the demineralized water is continuously and progressively removed, achieving the required deoxygenated water quality. The gases discharged from each vacuum lifter (including gas S-9A discharged when the first-stage vacuum lifter 2A is operating, gas S-9B discharged when the second-stage vacuum lifter 2B is operating, gas S-9C discharged when the third-stage vacuum lifter 2C is operating, and gas S-9D discharged when the fourth-stage vacuum lifter 2D is operating) are combined into gas S-10 and discharged into the atmosphere. Gas S-11 discharged into the atmosphere includes removed oxygen and nitrogen, etc. The inlet temperature of the demineralized water S-1 is 20℃ to 40℃, and the inlet pressure is 0.3MPag to 1.0MPag, which can be adjusted according to production requirements.

[0051] After passing the deoxygenation test, the deoxygenated water S-7 enters the multi-stream heat exchanger 30, where it undergoes deep heat exchange sequentially with the heat transfer medium water S-19 in the first heat exchange section 3A and with a portion of the initial heat transfer medium water S-16 in the second heat exchange section 3B. The temperature of the deoxygenated water S-12 after heat exchange is heated to 70℃ to 90℃, and then it enters the working fluid heat exchanger 40, where it undergoes deep heat exchange with the high-temperature, high-pressure working fluid S-24. This raises the temperature of the deoxygenated water S-13 exiting the working fluid heat exchanger 40 to 104℃ to 156℃, meeting the needs of users at different temperature levels. Then, through the action of the booster pump 44, qualified deoxygenated water S-14 is output with a pressure ranging from 0.2MPag to 10MPag. The temperature of the output qualified deoxygenated water S-14 can be adjusted within the range of 104℃ to 156℃ according to production requirements, and the pressure can also be adjusted within the range of 0.2MPag to 10MPag according to production requirements.

[0052] The gas-liquid mixed working fluid S-22 exchanges heat with the initial portion of the heat transfer medium S-17 in the working fluid evaporator 50. The gaseous working fluid S-23 evaporates and rises to the set temperature, then enters the compressor 60, which pressurizes the low-temperature, low-pressure gaseous working fluid S-23 to the set pressure, forming a high-temperature, high-pressure gaseous working fluid S-24. This then enters the working fluid heat exchanger 40, where it condenses and cools down to the set temperature. The working fluid S-25 discharged from the working fluid heat exchanger 40 is depressurized to the set pressure through the throttling expansion valve K, becoming a gas-liquid mixed working fluid S-22, which then enters the working fluid evaporator 50, forming a near-Lorentz cycle for the working fluid. The preferred working fluid is a non-azeotropic ternary environmentally friendly working fluid containing the following components: 5% to 35% by mass of R1234ze(e) (trans-1,3,3,3-tetrafluoropropylene, CAS No.: 29118-24-9), 10% to 15% by mass of R245fa (pentafluoropropane, CAS No.: 460-73-1), and 50% to 85% by mass of R1233zd (trans-1-chloro-3,3,3-trifluoropropylene, CAS No.: 102687-65-0). This ensures that the GWP (Global Warming Potential) does not exceed 150. In actual application, the formula can be adjusted within the range according to the temperature requirements of the deoxygenated water.

[0053] The heat transfer medium S-15 serves as the heat source and is input in two streams. One stream, S-16, enters the second heat exchange section 3B of the multi-stream heat exchanger 30, where it exchanges heat with deoxygenated water S-7 after deoxygenation. The other stream, S-17, enters the working fluid evaporator 50, where it first exchanges heat with the gaseous working fluid S-23. After the heat exchange, the heat transfer medium S-19 enters the first heat exchange section 3A of the multi-stream heat exchanger 30, where it exchanges heat a second time with the deoxygenated water S-7. Finally, the heat transfer medium S-18 discharged from the second heat exchange section 3B and the heat transfer medium S-20 discharged from the first heat exchange section 3A merge to form the heat transfer medium return water S-21, which returns upstream. The inlet temperature of the heat transfer medium S-15 is 70℃ to 95℃, and the return temperature is 50℃ to 80℃, which can be adjusted according to production requirements.

[0054] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0055] Cases 1 to 3 present the energy consumption and cost of producing deoxygenated water at temperatures ranging from 104°C to 156°C. They also compare the energy consumption and cost of thermal deoxygenation technology and conventional heat pump waste heat upgrade. The energy prices are calculated as follows: electricity price is 0.6 yuan / kW, steam price is 250 yuan / t, the energy conversion factor is 0.23 for electricity, and steam prices are calculated as 66 for 0.4 MPa and 76 for 1.0 MPa. The details are shown in Table 1 below.

[0056] Table 1

[0057] After the implementation of this invention, zero steam consumption deoxygenation can be achieved, and the energy consumption and cost of deoxygenated water are lower. The invention produces deoxygenated water at temperatures ranging from 104°C to 156°C. The power consumption per ton of deoxygenated water is 3.6 kW / t to 21.2 kW / t, equivalent to a deoxygenated water cost of RMB 2.2 / t to 12.7 / t and an energy consumption of 0.8 kgEO / t to 4.9 kgEO / t, respectively. This is significantly superior to thermal deoxygenation technology (deoxygenated water cost of RMB 13.4 / t to 43.1 / t and energy consumption of 3.5 kgEO / t to 13.1 kgEO / t), reducing deoxygenated water cost by 70.4% to 83.7% and energy consumption by 62.7% to 76.4%. It is also superior to conventional heat pump waste heat upgrade technology (deoxygenated water cost of RMB 3.3 / t to 18.5 / t and energy consumption of 1.3 kgEO / t to 7.1 kgEO / t), reducing deoxygenated water cost by 27.5% to 34.8% and energy consumption by 27.5% to 34.8%. This invention achieves zero steam consumption deoxygenation, producing boiler feedwater with qualified dissolved oxygen and temperature. The deoxygenation cost and energy consumption are lower than traditional processes, resulting in significant energy-saving benefits.

[0058] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A zero-steam-consumption boiler feedwater waste heat utilization system, characterized in that, include: A vacuum lifting deoxygenation unit is connected to the demineralized water inlet. The vacuum lifting deoxygenation unit includes multiple vacuum lifters connected in series, wherein the series nodes of adjacent vacuum lifters are also connected to the demineralized water inlet via a main water inlet pipeline. A multi-flow heat exchanger includes a first heat exchange section and a second heat exchange section, which respectively include a deoxygenated water pipeline and a heat source pipeline. The deoxygenated water pipelines of the first heat exchange section and the second heat exchange section are connected, and the heat source pipelines are independent of each other. The working fluid heat exchanger includes a deoxygenated water pipeline and a first working fluid pipeline. The outlet of the vacuum lifting deoxygenation unit is connected to the deoxygenated water outlet in sequence through the deoxygenated water pipeline of the first heat exchange section, the deoxygenated water pipeline of the second heat exchange section, and the deoxygenated water pipeline. The working fluid evaporator includes a heat source pipeline and a second working fluid pipeline. One end of the heat source pipeline is connected to a heat source inlet, and the other end is connected to a heat source return outlet via the heat source pipeline of the first heat exchange section. The heat source inlet is also connected to the heat source return outlet via the heat source pipeline of the second heat exchange section. The second working fluid pipeline and the first working fluid pipeline form a working fluid circulation pipeline.

2. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, Each of the vacuum lifters has an inlet and an outlet, wherein the outlet of the preceding vacuum lifter is connected in series with the inlet of the following vacuum lifter, and the series connection node between the inlet of the first vacuum lifter and the outlet of the preceding vacuum lifter and the inlet of the following vacuum lifter is connected to the demineralized water inlet via the main water inlet pipeline.

3. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, Each of the vacuum lifters also has an air inlet and an air outlet, with the air inlet of each vacuum lifter connected to an inert gas inlet and the air outlet of each vacuum lifter connected to a vacuum pump.

4. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 3, characterized in that, The inert gas is nitrogen, and the purity of the nitrogen is greater than or equal to 99.9%.

5. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, Also includes: A filter is connected between the demineralized water inlet and the vacuum lifting deoxygenation unit.

6. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, Also includes: The compressor is connected in the pipe from the second working fluid pipeline to the first working fluid pipeline; A throttling expansion valve is connected in the pipeline from the first working fluid pipeline to the second working fluid pipeline.

7. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, Also includes: A booster pump is connected between the deoxygenated water pipeline and the deoxygenated water outlet.

8. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, The working fluid flowing in the working fluid circulation pipeline is a non-azeotropic working fluid, which contains the following components: 5% to 35% by mass of trans-1,3,3,3-tetrafluoropropene, 10% to 15% by mass of pentafluoropropane, and 50% to 85% by mass of trans-1-chloro-3,3,3-trifluoropropene.

9. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, The temperature of the demineralized water entering the demineralized water inlet is 20°C to 40°C, and the pressure is 0.3 MPa to 1.0 MPa. The temperature of the heat transfer water entering the heat source inlet is 70°C to 95°C, and the temperature of the heat transfer water flowing out of the heat source return outlet is 50°C to 80°C.

10. The zero-steam-consumption boiler feedwater waste heat utilization system as described in claim 1, characterized in that, The temperature of the deoxygenated water flowing out of the multi-stream heat exchanger is 70°C to 90°C, and the temperature of the deoxygenated water flowing out of the deoxygenated water outlet is 104°C to 156°C, with a pressure of 0.2 MPa to 10 MPa.

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