Steam energy saving system with pressure matching device and heat source replacement

Abstract

The application discloses a steam energy-saving system with pressure matching device and heat source replacement, and relates to the field of comprehensive utilization of thermal energy in petrochemical industry. The steam energy-saving system comprises a steam production device, a pressure matching device, a low-grade steam pipe network, a high-grade steam pipe network and a hot water pipe network. The low-grade steam pipe network and the high-grade steam pipe network are connected with different steam production devices so that the steam pressure output by the low-grade steam pipe network is smaller than the steam pressure output by the high-grade steam pipe network. The low-grade steam pipe network and the high-grade steam pipe network are connected with the pressure matching device. The pressure matching device adjusts the proportion of the input steam of the low-grade steam pipe network and the high-grade steam pipe network so that the steam pressure output by the outlet of the pressure matching device is the target pressure. The hot water pipe network is connected with one or more heat users. The steam system energy efficiency of the petrochemical plant is improved, and the deep utilization of waste heat resources is realized, so that the efficiency and economic benefits are improved.

Description

Technical Field

[0001] This utility model relates to the field of comprehensive utilization of thermal energy in the petrochemical industry, specifically to an energy-saving renovation scheme for the steam system of a petrochemical plant that optimizes multi-source steam parameters through a pressure matching device and integrates low-grade heat sources. It is particularly suitable for energy-saving upgrades of the steam pipeline network of existing petrochemical plants. Background Technology

[0002] In the planning of steam pipeline networks in petrochemical plants, the level and classification of the entire plant's steam pipeline network, as well as the steam parameter range and design temperature and pressure of each pipeline network, are usually determined based on the needs of each process unit and system unit facility in the plant, such as ultra-high pressure steam, high pressure steam, medium pressure steam, and low pressure steam.

[0003] The following technical defects exist in the steam pipeline network system of petrochemical enterprises:

[0004] In existing technologies, when the steam parameters at the user end do not match the pipeline network parameters, a desuperheating and pressure-reducing device is commonly used for parameter adjustment. Using steam with parameters higher than those specified by the user, and then supplying it to the user after desuperheating and pressure reduction, will result in some heat loss; conversely, if steam with parameters lower than those specified by the user is used, its pressure and temperature will not meet the requirements. Patent CN222480457U discloses a steam system for an acrylic acid plant, which reduces the pressure of 2.0 MPa steam to a constant temperature of 1.5 MPa by adding a pressure-reducing valve and a desuperheating and pressure-reducing device. While this improves the problem of turbine steam superheat, it does not solve the irreversible losses during the pressure reduction process.

[0005] Patent CN210637124U discloses a comprehensive utilization device for steam of different pressure levels in a petrochemical plant. It proposes to use a pressure matching device to inject saturated exhaust steam to reduce high-pressure steam consumption. However, its design requires the construction of a new steam pipeline network, and the boiler parameters need to be adjusted simultaneously during the modification, resulting in low feasibility for modifying the existing device.

[0006] On the other hand, petrochemical enterprises generally possess a large amount of unutilized medium- and low-temperature hot water resources (≥80℃), such as steam condensate and process cooling water, whose thermal parameters can meet the heat demands of some low-grade steam users. Taking the MTBE unit as an example, the bottom temperature of the butene-1 refining tower only needs to be maintained at 65℃, but in actual operation, 0.4MPa low-pressure saturated steam is used for heating, resulting in a waste of approximately 90℃ of superheat.

[0007] In summary, the shortcomings of the existing solution are: 1) Waste of energy grade, as high-grade steam is supplied to low-demand users after pressure reduction, resulting in... 1) Inefficient. 2) Insufficient system flexibility and scalability, and low feasibility of modifying existing equipment. 3) Waste heat resources are idle, and a large amount of hot water is not effectively utilized. Utility Model Content

[0008] The technical problem addressed in this application is to overcome the problems of large irreversible losses, low waste heat utilization, and poor compatibility in existing steam decompression technologies. It provides a steam energy-saving system and retrofit method that utilizes a pressure matcher in conjunction with heat source substitution. This is achieved by constructing a tiered energy system that replaces steam with hot water, while simultaneously optimizing steam energy levels using a pressure matcher. This eliminates thermodynamic losses during decompression, achieving a dual breakthrough in improving the energy efficiency of petrochemical plant steam systems and deeply utilizing waste heat resources, thereby increasing... Efficiency and economic benefits.

[0009] Furthermore, it is compatible with low-cost energy-saving retrofits of new plants and existing facilities, and constructs a multi-source steam collaborative system with a pressure matcher as the core. By releasing low-grade steam resources through heat source substitution and integrating low-grade steam resources to release high-grade steam resources, it achieves matching of high and low grade steam and deep utilization of waste heat.

[0010] The technical solution provided in this application is as follows:

[0011] A steam energy-saving system and retrofitting method for pressure matching and heat source substitution, including steam production equipment, pressure matching, low-grade steam network, high-grade steam network and hot water network;

[0012] Among the equipment that requires heating, equipment whose required temperature is lower than the hot water temperature in the factory's hot water pipe network is defined as a heat user, and equipment whose required temperature is higher than the required temperature of a heat user is defined as a steam user.

[0013] The high-grade steam network contains purchased high-grade steam, while the low-grade steam network connects to the steam production equipment. The steam pressure output from the low-grade steam network is lower than that output from the high-grade steam network.

[0014] Both the low-grade steam network and the high-grade steam network are connected to a pressure matcher. The pressure matcher adjusts the ratio of steam input to the low-grade steam network and the high-grade steam network to make the steam pressure output from the pressure matcher outlet the target pressure.

[0015] The hot water pipe network is connected to one or more heat users. The heat source temperature of the hot water pipe network needs to be higher than the temperature required by the heat users. Low-grade steam is saved by replacing the heat source.

[0016] Furthermore, the hot water pipe network connects to one or more heat users via one or more branches of the fourth pipe. The heat source temperature of the hot water pipe network is higher than the temperature required by the heat users, thus saving low-grade steam through heat source substitution.

[0017] Furthermore, the pressure matcher is equipped with an intake steam inlet, a drive steam inlet, and a mixed steam outlet. The low-grade steam to be replaced is transported to the intake steam inlet of the pressure matcher via a first pipeline. Steam from the high-grade steam network is transported to the drive steam inlet of the pressure matcher via a second pipeline. The high and low-grade steam exchange energy within the pressure matcher, increasing the pressure of the low-grade steam to meet the user's pressure requirements. The mixed steam is then connected to the steam user's end via a third pipeline from the pressure matcher outlet.

[0018] Furthermore, a pressure transmitter is installed in the third pipeline, and an actuator is provided in the pressure matching device. The pressure transmitter is connected to the actuator of the pressure matching device. The pressure transmitter is used to detect the steam pressure in the third pipeline and send the detection result to the actuator. The actuator adjusts the steam ratio of the low-grade steam network and the high-grade steam network input to the pressure matching device according to the detection result. The pressure transmitter and the actuator of the pressure matching device form a closed-loop control to ensure that the output steam pressure accurately matches the steam user's needs.

[0019] Furthermore, the steam pressure required by the steam user is higher than the steam pressure of the low-grade steam network but lower than the steam pressure of the high-grade steam network.

[0020] Furthermore, the steam pressure of the low-grade steam network is lower than that of the high-grade steam network.

[0021] The steam pipeline system can encompass pipeline combinations with different pressure gradients, as exemplified below: Low-grade steam pipelines and high-grade steam pipelines can be combinations of low-pressure and medium-pressure steam pipelines, or medium-pressure and high-pressure steam pipelines, or ultra-high-pressure and high-pressure steam pipelines. The steam pressure of the low-pressure steam pipeline is less than 1 MPa; the steam pressure of the medium-pressure steam pipeline is greater than 1 MPa and less than 4 MPa; the steam pressure of the high-pressure steam pipeline is greater than 4 MPa and less than 10 MPa; and the steam pressure of the ultra-high-pressure steam pipeline is greater than 10 MPa. It should be noted that the operating parameters and aforementioned numerical ranges of the low-grade and high-grade steam pipelines are only quantitative representations of typical application scenarios, and those skilled in the art can adjust these parameters according to actual needs. This invention, through the dynamic control mechanism of the pressure matcher, can adapt to any combination of steam pipelines with pressure gradients and is not absolutely limited by the example values.

[0022] The retrofit method for a steam energy-saving system using a pressure matcher in conjunction with heat source replacement in an existing petrochemical plant is as follows: A new fourth pipeline connecting to the hot water network is constructed to replace the original connecting pipeline for the low-grade steam network used by the heat users. A pressure matcher and its associated piping are added, connecting the high-grade steam network, the low-grade steam network, and the steam users. A pressure transmitter is installed on the connecting pipeline between the pressure matcher and the steam users to ensure that the output steam pressure matches the steam user's needs.

[0023] In summary, this application includes at least the following beneficial technical effects:

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1) This invention replaces the traditional desuperheating and depressurization device with a pressure matching device, utilizing high-grade steam to induce low-grade steam to generate target pressure steam, thereby improving... It improves efficiency and saves high-grade steam.

[0026] 2) This invention constructs a low-grade heat source replacement system with temperature gradient adaptation, using hot water to replace low-grade steam. The replaced steam is mixed with high-grade steam and pressurized through a pressure matching device, forming an energy-optimized path for low-grade steam to replace high-grade steam, thereby improving the utilization rate of the entire plant's steam network.

[0027] 3) This utility model is based on the actuator and PID control module to adjust the pressure matching device. The adjustment is flexible and the output steam pressure can be continuously adjusted in the range of low-grade steam and high-grade steam, which meets the pressure matching needs of steam users who originally relied on desuperheating and pressure reducing devices.

[0028] 4) This utility model is universally applicable to engineering implementation, suitable for optimizing the design of new plants, reducing the rated load of high-grade steam boilers, and reducing initial investment costs. Existing projects only require the addition of pressure matching devices and supporting piping networks, achieving steam network upgrades while maintaining the original boiler operating parameters, resulting in low investment costs and significant energy-saving effects. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the steam energy-saving system and modification method for pressure matching device-coordinated heat source replacement described in this utility model.

[0030] Figure 2 This is a schematic diagram of the pressure matching device described in this utility model.

[0031] Figure 3 This is a schematic diagram of an existing petrochemical plant steam system.

[0032] Explanation of reference numerals in the attached diagram: 1. Pressure matching device; 2. First pipeline; 3. Low-grade steam network; 4. Second pipeline; 5. High-grade steam network; 6. Third pipeline; 7. Steam user; 8. Pressure transmitter; 9. Heat user; 10. Fourth pipeline; 11. First branch of fourth pipeline; 12. Hot water network; 13. Heat user; 14. Second branch of fourth pipeline; 15. Steam inlet for pressure matching device; 16. Steam inlet for pressure matching device; 17. Outlet for pressure matching device; 18. Actuator; 19. Desuperheater and pressure reducer; 20. Desuperheating water pipeline; 21. First branch of first pipeline; 22. Second branch of first pipeline. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments disclosed in this application will be described in further detail below with reference to the accompanying drawings.

[0034] This application primarily addresses the modification of existing steam pipeline networks in factories that utilize desuperheating and pressure reducing devices. The low-grade steam pipeline connects to steam production equipment (such as boilers) within the factory, while the high-grade steam pipeline carries externally purchased high-grade steam. The steam pipeline network supplies heat to equipment within the factory's production system that requires heating. Among the equipment requiring heating, those with a temperature requirement lower than the hot water temperature in the factory's hot water pipeline are defined as heat users, while those with a temperature requirement higher than the heat user's temperature are defined as steam users 7. Both heat users and steam users 7 in the steam pipeline network using desuperheating and pressure reducing devices utilize high-grade steam and / or low-grade steam for heating.

[0035] For existing factories, since the low-grade steam pipeline network connecting to steam production equipment (such as boilers) is already designed and installed, the output and pressure of the low-grade steam produced by the factory's steam production equipment are relatively fixed, and the output of low-grade steam is designed according to the needs of the production system. For example, a factory can produce a type of steam at a lower fixed pressure, and the output of this type of fixed-pressure steam fluctuates little within the design range. The factory also purchases a type of steam at a higher fixed pressure. When the temperature required by the equipment needing heat supply differs from the fixed pressure of the steam produced by the factory, it is necessary to adjust the steam to the required pressure based on the existing fixed-pressure steam.

[0036] This application employs a pressure matching device 1, which combines two existing fixed-pressure steam sources (low-grade steam and high-grade steam) for regulation, obtaining steam at the target pressure at the outlet of pressure matching device 1. However, due to the modification, the originally produced low-grade steam has its own uses, and there is insufficient low-grade steam to work with the high-grade steam pipe to regulate the steam to the target pressure. Therefore, this application utilizes the hot water from hot water pipe network 12 to supply heat to users, thereby using more low-grade steam for pressure matching device 1, that is, saving low-grade steam through heat source substitution. The purpose of the modification is achieved: by replacing low-grade steam with hot water from hot water pipe network 12, and using high-grade steam to induce low-grade steam to generate target pressure steam, high-grade steam is saved, thus saving the cost of purchasing high-grade steam.

[0037] Reference Figure 1 and Figure 2 As shown in the embodiments of this application, a steam energy-saving system and modification method for pressure matching and heat source substitution are proposed, including: a pressure matching device 1, a low-grade steam network 3, a high-grade steam network 5, a hot water network 12, steam users 7, heat users, and connecting pipes. The connecting pipes include a first pipe 2, a second pipe 4, a third pipe 6, and a fourth pipe 10. The high-grade steam network 5 contains purchased high-grade steam, and the low-grade steam network 3 is connected to steam production equipment. The steam pressure provided by the low-grade steam network 3 is lower than that provided by the high-grade steam network 5. The heat source medium of the hot water network 12 comes from hot water used up by boilers and / or other equipment (other equipment includes heat exchangers, etc.). The hot water network 12 has one or more branches, and the temperatures of different branches may be the same or different, thereby meeting the needs of heat users with different temperature requirements.

[0038] The pressure matching device 1 has its intake steam inlet 15 connected to the low-grade steam network 3 via a first pipe 2, its drive steam inlet 16 connected to the high-grade steam network 5 via a second pipe 4, and its mixed steam outlet 17 connected to the steam user 7 via a third pipe 6. A pressure transmitter 8 is installed on the third pipe 6 and connected to the pressure matching device actuator 18.

[0039] Hot water pipe network 12 connects to one or more heat users through the fourth pipe 10. The heat source temperature of hot water pipe network 12 needs to be higher than the temperature required by the heat users, and low-grade steam is saved through heat source substitution. In this embodiment, there are two heat users, namely heat user 9 and heat user 13. Hot water pipe network 12 provides heat source to heat users 9 and 13 through the first branch 11 and the second branch 14 of the fourth pipe 10, respectively.

[0040] The low-grade steam network 3 and the high-grade steam network 5 can be a combination of a low-pressure steam network and a medium-pressure steam network, or a combination of a medium-pressure steam network and a high-pressure steam network. The steam pressure of the low-pressure steam network is less than 1 MPa, the steam pressure of the medium-pressure steam network is greater than 1 MPa and less than 3.5 MPa, and the steam pressure of the high-pressure steam network is greater than 4 MPa.

[0041] The steam pressure required by steam user 7 is higher than the steam pressure of the low-grade steam network but lower than the steam pressure of the high-grade steam network.

[0042] The heat source temperature of hot water pipe network 12 is greater than the temperature required by the heat users.

[0043] The specific working process of this utility model is as follows:

[0044] Hot water from hot water pipe network 12 is delivered to heat users 9 and 13 via the first branch 11 and the second branch 14 of the fourth pipe 10. The hot water from the hot water pipe network serves as a heat source to replace the steam from the low-grade steam pipe network 3 in the existing technology, thus saving on the consumption of low-grade steam.

[0045] The saved low-grade steam is transported to the pressure matching unit's intake steam inlet 15 via the first pipeline 2. Steam from the high-grade steam network 5 is transported to the pressure matching unit's drive steam inlet 16 via the second pipeline 4. The low-grade steam within the pressure matching unit 1 is pressurized and output from the outlet 17. A third pipeline 6 connects to the pressure matching unit's outlet 17 and is equipped with a pressure transmitter 8. The pressure transmitter 8 adjusts its internal structure according to the pressure required by the steam user 7 via the pressure matching unit's actuator 18 to change the flow rate of the high-grade steam, ensuring that the pressure at the pressure matching unit's outlet 17 meets the user's requirements.

[0046] This technical solution constructs a low-grade heat source replacement system, using hot water to replace low-grade steam, and then uses a pressure matching device to pressurize the waste heat-replaced low-grade steam and supply it to steam user 7, thereby saving high-grade steam consumption.

[0047] This application also proposes a modification method for a steam energy-saving system and modification method that uses a pressure matching device to coordinate heat source replacement, including:

[0048] Reference Figure 1 , Figure 3As shown, when the production system is an MTBE (methyl tert-butyl ether) and butadiene unit, specifically taking an existing MTBE and butadiene unit in a petrochemical plant as an example, the heat users 9 and 13 (butene-1 reboiler) of the MTBE unit originally used low-pressure steam (0.4 MPa) from the low-grade steam network 3 to maintain the temperature (65°C). The butadiene unit originally used medium-pressure steam (1 MPa) from the high-grade steam network 5 and desuperheating water from the hot water network 12 for desuperheating and pressure reduction in the desuperheater and pressure reducer 19, outputting steam (0.75 MPa) to supply steam user 7 (stripping tower reboiler).

[0049] In this embodiment, the first pipe 2 connecting heat user 9, heat user 13, and low-grade steam network 3 is replaced with a fourth pipe 10 connecting to hot water network 12. By connecting to hot water network 12, hot water (90℃) is used instead of steam as the heat source, saving 20 tons of low-pressure steam per hour.

[0050] In this embodiment, a new pressure matching unit 1 is added. Its steam inlet 15 is connected to the low-grade steam network 3 via a first pipe 2, and its outlet 17 is connected to the steam user 7 via a third pipe 6. The 20 t / h of low-pressure steam being replaced enters the pressure matching unit 1 via the first pipe 2, mixing with medium-pressure steam (1.0 MPa) from the high-grade steam network 5. The pressure matching unit 1 dynamically adjusts the mixing ratio of high and low-grade steam via an actuator 18, outputting 0.75 MPa steam to supply the stripping tower reboiler. Compared to the original scheme using a desuperheater / pressure reducer 19 to reduce the pressure of high-grade steam before supplying it to the stripping tower reboiler, this embodiment saves 20 tons of medium-pressure steam per hour.

[0051] This utility model's steam energy-saving system achieves a dual breakthrough in energy efficiency improvement and applicability for energy-saving retrofits through a pressure matching device and coordinated heat source cascade reconfiguration. Its specific technical advantages compared to existing technologies are as follows:

[0052] 1) Energy Grade Optimization: This invention uses a pressure matching device to replace the traditional desuperheating and depressurization device, eliminating steam grade loss during depressurization and saving high-grade steam. Taking Example 1 as an example, the pressure matching device mixes high-grade steam and low-grade steam to optimize the target steam grade. Efficiency increased from 52.3% in the traditional scheme to 78.6%, saving 20t / h of medium-pressure steam.

[0053] 2) Heat Source Cascade Replacement: This invention constructs a low-grade heat source replacement system with temperature gradient adaptation, using hot water to replace low-grade steam. The replaced steam is mixed with high-grade steam and pressurized via a pressure matcher, forming an energy-optimized path for low-grade steam to replace high-grade steam, thereby improving the utilization rate of the entire plant's steam network. Taking Example 1 as an example, in the MTBE unit, 90℃ hot water replaces low-pressure steam, and the low-pressure steam is pressurized via a pressure matcher and supplied to steam users, saving 20t / h of medium-pressure steam.

[0054] 3) Flexible pressure regulation: This utility model forms a closed-loop regulation system by having the actuator of the pressure matching device work in conjunction with the outlet pressure PID control module. The output steam pressure can be continuously adjusted within the range of input low-grade steam and high-grade steam, meeting the energy adaptation needs of steam users in petrochemical plants that previously required pressure reduction (such as stripping towers, distillation towers, etc.).

[0055] 4) Wide applicability: This utility model is compatible with both new and existing plant steam system upgrades. New projects can reduce the load on medium-pressure boilers and reduce initial investment; upgrades to existing projects only require the addition of pressure matching devices and supporting piping networks, achieving steam network upgrades while maintaining the original boiler operating parameters, resulting in low investment costs and significant energy-saving effects.

[0056] The contents not described in detail in this application specification are common knowledge to those skilled in the art.

[0057] The present application has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present application. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present application without departing from the spirit and scope of the present application, and all such modifications and improvements fall within the scope of the present application. The scope of protection of the present application is determined by the appended claims.

Claims

1. A steam energy-saving system for pressure matching and heat source substitution, characterized in that: It includes steam production equipment, pressure matching device (1), low-grade steam pipeline (3), high-grade steam pipeline (5) and hot water pipeline (12); Among the equipment that requires heating, the equipment whose required temperature is lower than the hot water temperature in the hot water pipe network (12) in the factory is defined as a heat user, and the equipment whose required temperature is higher than the required temperature of the heat user is defined as a steam user (7). The high-grade steam network contains high-grade steam, while the low-grade steam network (3) is connected to the steam production equipment; the steam pressure output by the low-grade steam network (3) is less than the steam pressure output by the high-grade steam network (5); Both the low-grade steam network (3) and the high-grade steam network (5) are connected to the pressure matching device (1). The pressure matching device (1) adjusts the flow rate of the steam input to the low-grade steam network (3) and the high-grade steam network (5) so that the steam pressure output from the outlet of the pressure matching device (1) is the target pressure. The hot water pipe network (12) is connected to one or more heat users. The heat source temperature of the hot water pipe network (12) needs to be higher than the temperature required by the heat users. Low-grade steam is saved by heat source substitution.

2. The steam energy-saving system for pressure matching device-assisted heat source replacement according to claim 1, characterized in that: The pressure matching device (1) is provided with a steam intake inlet (15), a steam drive inlet (16) and a mixed steam outlet (17). The steam intake inlet (15) is connected to the low-grade steam network (3) through the first pipe (2), the steam drive inlet (16) is connected to the high-grade steam network (5) through the second pipe (4), and the mixed steam outlet (17) is connected to the steam user (7) through the third pipe (6).

3. The steam energy-saving system for pressure matching device-assisted heat source replacement according to claim 2, characterized in that: The third pipeline (6) is equipped with a pressure transmitter (8), and the pressure matching device (1) is equipped with an actuator (18). The pressure transmitter (8) is connected to the actuator (18) of the pressure matching device. The pressure transmitter (8) is used to detect the steam pressure in the third pipeline (6) and send the detection result to the actuator (18). The actuator (18) adjusts the steam ratio of the low-grade steam network (3) and the high-grade steam network (5) input to the pressure matching device (1) according to the detection result.

4. The steam energy-saving system for pressure matching device-assisted heat source replacement according to claim 1, characterized in that: The steam user (7) requires a steam pressure higher than that of the low-grade steam network (3) and lower than that of the high-grade steam network (5).

5. The steam energy-saving system for pressure matching device-assisted heat source replacement according to claim 1, characterized in that: The steam pressure of the low-grade steam network (3) is lower than that of the high-grade steam network (5).

6. The steam energy-saving system for pressure matching device-assisted heat source replacement according to claim 1, characterized in that: The low-grade steam network (3) and the high-grade steam network (5) are combinations of low-pressure steam network and medium-pressure steam network, or combinations of medium-pressure steam network and high-pressure steam network, or combinations of ultra-high-pressure steam network and high-pressure steam network; the steam pressure of the low-pressure steam network is less than 1 MPa; the steam pressure of the medium-pressure steam network is 1 MPa-4 MPa; the steam pressure of the high-pressure steam network is 4 MPa-10 MPa; and the steam pressure of the ultra-high-pressure steam network is greater than 10 MPa.

7. The steam energy-saving system for pressure matching device-assisted heat source replacement according to claim 1, characterized in that: The hot water pipe network (12) is connected to the fourth pipe (10), and the fourth pipe (10) is connected to multiple branches. The heat source temperatures at the outlets of different branches are the same or different, and the outlets of the branches are connected to the heat users.

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