Energy-saving type self-gravity condensation reflux efficient rectification system and control method

Abstract

The invention relates to the technical field of gas-liquid separation and purification, in particular to an energy-saving type self-gravity condensation reflux efficient rectification system and a control method. Comprising a buffer tank, a feeding pump, a feeding and discharging thermal coupling heat exchanger, an efficient rectifying tower, a self-gravity reflux condenser, a tower bottom reboiler and a tower bottom extraction pump, the self-gravity reflux condenser is arranged at the top of the high-efficiency rectifying tower, the feeding and discharging thermal coupling heat exchanger is connected between the buffer tank and a feeding hole of the high-efficiency rectifying tower, a tower bottom outlet of the high-efficiency rectifying tower is connected with the tower bottom reboiler and an inlet of the tower bottom extraction pump, and an outlet of the tower bottom reboiler is connected with a circulating feeding hole of the high-efficiency rectifying tower; the self-gravity reflux condenser is used for condensing the tower top gas phase part into liquid, and the liquid flows back to the efficient rectifying tower through gravity; the feeding and discharging thermal coupling heat exchanger is used for exchanging heat between the raw material output by the buffer tank and a tower bottom product of the efficient rectifying tower; and the tower bottom extraction pump is used for outputting tower bottom products. Resource waste is avoided, and equipment investment and occupied area are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of gas-liquid separation and purification, and in particular to an energy-saving gravity condensation reflux high-efficiency distillation system and a control method. Background Art

[0002] Distillation is a common and efficient separation method in the chemical and pharmaceutical industries. It utilizes the different volatilities of the components in a mixture to separate them. Distillation is typically performed in a distillation tower, where the gas and liquid phases meet in countercurrent flow, allowing for interphase heat and mass transfer. It has widespread applications in numerous fields, including petroleum refining, fine chemicals, pharmaceuticals, and environmental protection.

[0003] Typical distillation equipment includes distillation towers, reboilers, and condensers. Traditional distillation processes require a continuous supply of industrial steam to heat the tower bottom liquid, generating rising steam to propel the distillation process. Furthermore, the light component secondary steam generated by the system must be cooled, condensed, and then refluxed through the condenser. This process creates a significant amount of latent heat that is difficult to reuse, resulting in wasted resources. As steam costs continue to rise, operating costs also increase.

[0004] In addition, the existing distillation tower structure is relatively simple. When dealing with some complex systems or requiring high separation accuracy, a higher tower body and a larger number of theoretical plates are often required, resulting in large equipment investment and floor space, and the separation effect is not satisfactory.

[0005] For the distillation process, which consumes a lot of energy, how to improve energy utilization efficiency, reduce energy waste, and achieve breakthroughs in energy-saving technologies has become a key issue facing the chemical, pharmaceutical and other industries in the production process.

[0006] To address the energy consumption issues of traditional distillation processes, several technologies have been proposed and applied. However, these existing energy-saving technologies may suffer from limited applicability, complex equipment, high investment costs, or insignificant energy savings, making them difficult to meet the widespread demand for efficient, energy-saving, and low-cost distillation technologies in industrial production.

[0007] Therefore, the development of a new energy-saving gravity condensation reflux high-efficiency distillation system and control method is of great practical significance for improving the energy utilization efficiency of the distillation process, reducing costs and reducing environmental pollution. Summary of the Invention

[0008] In view of this, the embodiments of the present application provide an energy-saving gravity condensation reflux high-efficiency distillation system and control method. By setting the condenser at the top of the distillation tower, the top gas phase is partially cooled and refluxed in the gravity reflux condenser at the top of the distillation tower. The reflux amount can be controlled by the refrigerant temperature and flow of the condenser, thereby avoiding waste of resources and reducing equipment investment and floor space.

[0009] A first aspect of the embodiments of the present application provides an energy-saving gravity condensation reflux high-efficiency distillation system, comprising:

[0010] Buffer tank, feed pump, feed and discharge thermal coupling heat exchanger, high-efficiency distillation tower, gravity reflux condenser, tower bottom reboiler and tower bottom extraction pump;

[0011] The gravity reflux condenser is arranged at the top of the high-efficiency distillation tower and is connected to the high-efficiency distillation tower, the inlet and outlet heat coupling heat exchanger is connected between the buffer tank and the feed inlet of the high-efficiency distillation tower, the bottom outlet of the high-efficiency distillation tower is connected to the bottom reboiler and the inlet of the bottom extraction pump, and the outlet of the bottom reboiler is connected to the circulation feed inlet of the high-efficiency distillation tower;

[0012] The gravity reflux condenser is used to condense the gas phase at the top of the tower into liquid and reflux it to the high-efficiency distillation tower by gravity; the inlet and outlet thermal coupling heat exchanger is used to exchange heat between the raw materials output from the buffer tank and the bottom product of the high-efficiency distillation tower; the bottom extraction pump is used to output the bottom product.

[0013] A second aspect of the embodiments of the present application provides a control method for an energy-saving gravity condensation reflux high-efficiency distillation system, comprising:

[0014] After being buffered in the buffer tank, the raw materials are pressurized by the feed pump, and then heat-exchanged with the bottom product in the feed and discharge heat coupling heat exchanger before entering the high-efficiency distillation tower;

[0015] The gas phase at the top of the tower enters the gravity reflux condenser for partial condensation, and the condensate flows back to the top of the tower by gravity, and the uncondensed gas phase is extracted as the top product;

[0016] The reboiler at the bottom of the tower heats the liquid in the tower kettle to generate rising steam, which participates in distillation. The bottom product is transported to the inlet and outlet thermal coupling heat exchanger through the bottom extraction pump and then discharged after heat exchange.

[0017] In the embodiment of the present application, a condenser is arranged at the top of the distillation tower, and the top gas phase is partially cooled and refluxed in the gravity reflux condenser at the top of the distillation tower. The reflux rate can be controlled by the refrigerant temperature and flow rate of the condenser, thereby avoiding waste of resources and recovering energy. This not only reduces energy consumption, but also effectively improves the purity of the top product and reduces equipment investment and floor space. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 It is a structural schematic diagram of an energy-saving gravity condensation reflux high-efficiency distillation system provided in one embodiment of the present application.

[0020] In the figure: 1-buffer tank, 2-feed pump, 3-inlet and outlet thermal coupling heat exchanger, 4-high-efficiency distillation tower, 5-gravity reflux condenser, 6-tower bottom reboiler, 7-tower bottom extraction pump. DETAILED DESCRIPTION

[0021] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0022] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0023] like Figure 1 As shown, the embodiment of the present application provides an energy-saving gravity condensation reflux high-efficiency distillation system, characterized by comprising:

[0024] Buffer tank 1, feed pump 2, feed and discharge thermal coupling heat exchanger 3, high-efficiency distillation tower 4, gravity reflux condenser 5, tower bottom reboiler 6 and tower bottom extraction pump 7;

[0025] The gravity reflux condenser 5 is arranged at the top of the high-efficiency distillation tower 4 and is connected to the high-efficiency distillation tower 4. The inlet and outlet heat coupling heat exchanger 3 is connected between the buffer tank 1 and the feed port of the high-efficiency distillation tower 4. The bottom outlet of the high-efficiency distillation tower 4 is connected to the inlet of the bottom reboiler 6 and the bottom extraction pump 7. The outlet of the bottom reboiler 6 is connected to the circulation feed port of the high-efficiency distillation tower 4.

[0026] The gravity reflux condenser 5 is used to condense the gas phase at the top of the tower into liquid and reflux it to the high-efficiency distillation tower 4 by gravity; the inlet and outlet thermal coupling heat exchanger 3 is used to exchange heat between the raw material output from the buffer tank 1 and the bottom product of the high-efficiency distillation tower 4; the bottom extraction pump 7 is used to output the bottom product.

[0027] The embodiment of the present application sets a condenser at the top of the distillation tower, and the top gas phase is partially cooled and refluxed in the gravity reflux condenser at the top of the distillation tower. The reflux amount can be controlled by the refrigerant temperature and flow of the condenser, thereby avoiding waste of resources. The high-efficiency top gravity condenser replaces the traditional top condenser, reflux tank, and reflux pump, which not only effectively saves equipment investment and floor space, but also effectively reduces the energy consumption of the separation process while improving the purity of the top product. Due to the high degree of equipment integration in the device and the small floor space, the workload of pipeline and equipment installation is reduced, which greatly improves the efficiency of device construction. At the same time, the amount of pipeline and valve installation is reduced, which can simplify operation and improve production efficiency, reduce misoperation, and reduce the risk of production accidents. Due to the low investment, small floor space, and short device construction period, the device has a very good application in the chemical industry and environmental protection fields, and it solves environmental protection problems well and brings considerable economic benefits.

[0028] In one embodiment, the cold side inlet of the inlet and outlet thermal coupling heat exchanger 3 is connected to the output end of the buffer tank 1, the cold side outlet is connected to the feed port of the high-efficiency distillation tower 4, the hot side inlet is connected to the outlet of the bottom extraction pump 7, and the hot side outlet is used to connect to the purified water system.

[0029] In application, the raw materials in the buffer tank 1 are transported by the feed pump 2 to the cold side inlet of the feed and discharge heat-coupled heat exchanger 3, where they are heated by heat exchange with the bottom material from the bottom extraction pump 7 at the hot side inlet. After the bottom material cools down by heat exchange, it can be connected to the purified water system for recovery.

[0030] This application implements direct heat exchange between the cold-side feedstock and the hot-side bottoms product, maximizing heat recovery efficiency and reducing external steam consumption required for feedstock preheating. The hot-side outlet is connected to a purified water system, further utilizing waste heat for other process steps, achieving cascaded energy utilization.

[0031] In one embodiment, the cold side inlet of the bottom reboiler 6 is connected to the bottom outlet of the bottom extraction pump 7, and the cold side outlet is connected to the circulation feed port of the high-efficiency distillation tower 4, and the heat source of the bottom reboiler 6 is high-temperature steam input from the outside.

[0032] In use, the produced material at the bottom outlet of the tower bottom extraction pump 7 is heated by heat exchange in the tower bottom reboiler 6 before re-entering the high-efficiency distillation tower 4 through the circulating feed port to participate in the reaction. The tower bottom reboiler 6 heats the produced material at the bottom outlet with high-temperature steam input from the outside, and the high-temperature steam is converted into condensate after heat exchange and output.

[0033] The tower bottom reboiler in this embodiment uses superheated steam as its heat source. This is connected to the tower bottom extraction pump via a cold-side loop, ensuring uniform heating and rapid vaporization of the tower bottom liquid, avoiding localized overheating and coking. The high heat transfer efficiency of superheated steam accelerates the reboiler's heat load response, shortening system startup time and enhancing operational stability.

[0034] In one embodiment, the gravity reflux condenser 5 is a partition-type heat exchanger, the refrigerant inlet and outlet of the gravity reflux condenser 5 are respectively connected to an external cold source, and the condensate outlet of the gravity reflux condenser 5 is connected to the top liquid phase distributor or the first tower plate of the high-efficiency distillation tower 4.

[0035] The gravity reflux condenser of the embodiment of the present application is a partition-wall heat exchanger, in which the refrigerant exchanges heat with the gas phase at the top of the tower via the partition wall, thereby preventing the refrigerant from contaminating the product. At the same time, the condensate directly refluxes to the liquid phase distributor at the top of the tower or the first tower plate, ensuring uniform reflux distribution and improving the separation efficiency of the light components at the top of the tower. In addition, the partition-wall structure reduces refrigerant consumption compared to direct contact condensation.

[0036] In one embodiment, the packing type of the high-efficiency distillation tower 4 is at least one of trays, structured packing or random packing.

[0037] The embodiments of this application allow for the flexible use of trays, structured packing, or random packing in high-efficiency distillation towers, optimizing mass transfer efficiency for different material characteristics (such as high viscosity and prone to scaling). For example, structured packing can reduce tower height by 30% and reduce pressure drop, while random packing is suitable for systems containing solid particles, expanding the system's applicability and compatibility with various industrial scenarios.

[0038] In one embodiment, the high-efficiency distillation tower 4 uses the following formula to dynamically adjust the heat load:

[0039] Q=f(F,η,n,T)

[0040] Where F is the feed flow rate, η is the packing efficiency, n is the number of theoretical plates, and T is the temperature.

[0041] The present invention provides a method for controlling an energy-saving gravity condensation reflux high-efficiency distillation system, comprising:

[0042] Step 1: After the raw materials are buffered in the buffer tank, they are pressurized by the feed pump and then enter the high-efficiency distillation tower after heat exchange with the bottom product through the inlet and outlet heat coupling heat exchanger.

[0043] In application, this control method is explained by taking the treatment of ammonia-containing wastewater by this system as an example. The acid gas composition of ammonia-containing wastewater in a multi-effect evaporation process is shown in the following table:

[0044]

[0045] The raw materials come from outside the boundary to the buffer tank. Under the operating conditions of temperature 40℃ and pressure 0.01~0.2MPaG, the raw materials are pressurized by the feed pump. The raw materials and the bottom products of the distillation tower are thermally coupled and heated to 120~150℃ using the inlet and outlet heat coupling heat exchangers. Then, they enter the high-efficiency distillation tower from the appropriate theoretical position.

[0046] Step 2: The gas phase at the top of the tower enters the gravity reflux condenser for partial condensation. The condensate flows back to the top of the tower by gravity, and the uncondensed gas phase is extracted as the top product.

[0047] In application, the operating pressure of the high-efficiency distillation tower is 0.3~1.2MPaG. The gas at the top of the tower enters the gravity reflux condenser and is partially condensed and refluxed by circulating water. The ammonia product with a purity greater than 99.5% is produced from the top of the gravity reflux condenser, and the production pipeline can be connected to the liquid ammonia system.

[0048] Step 3: The tower bottom reboiler heats the tower bottom liquid to generate rising steam, which participates in distillation. The tower bottom product is transported to the inlet and outlet thermal coupling heat exchanger through the tower bottom extraction pump and then discharged after heat exchange.

[0049] In application, the bottom of the high-efficiency distillation tower uses a bottom reboiler to provide heat source, and 1.5MPaG steam is used to heat and vaporize the raw materials. The bottom product of the tower is pressurized to 0.8~1.2MPaG by the bottom extraction pump, and then enters the product tank area after heat exchange and cooling through the inlet and outlet thermal coupling heat exchanger, which saves energy by more than 20% compared with traditional processes.

[0050] In one embodiment, it further includes:

[0051] The tower top temperature, tower bottom temperature, raw material flow and composition data are collected in real time, and the refrigerant flow, heat medium flow, tower top extraction valve and reflux valve opening are dynamically adjusted to enable the system to operate with the lowest energy consumption while meeting the separation conditions.

[0052] In application, a condenser is placed at the top of a distillation tower, partially condensing the overhead gas phase through the condenser. PID control is used for the overhead gas phase output. A cascade proportional-integral control is applied to the top temperature of the distillation tower and the flow rate of the refrigerant from the gravity reflux condenser. The top temperature is proportionally controlled with the refrigerant flow rate to achieve precise control of the top temperature of the distillation tower. The cumulative change in the top temperature of the distillation tower and the overhead output are proportionally controlled to maintain the stability of the overhead output flow rate. The bottom temperature of the distillation tower is cascaded proportional-integral controlled with the heat transfer medium. The bottom temperature of the distillation tower is proportionally controlled with the heat transfer medium flow rate to achieve precise control of the bottom temperature. The steam flow meter is integrally controlled with the steam control valve to achieve operational stability. By combining the composition and flow rate of the raw materials with the operating parameters of the distillation tower, partial differential equations are solved, and algorithmic control is used to thermally couple the entire process system.

[0053] The embodiment of the present application dynamically adjusts the valve opening and the flow of cold and hot media by collecting real-time data on the top / bottom temperature, raw material flow, and composition of the tower, forming a multivariable closed-loop control. This effectively controls the temperature balance and energy consumption level of the device, saving more than 15% of energy consumption compared to traditional distillation processes. Algorithm-controlled heat coupling is used. This not only reduces energy consumption and recovers energy, but also effectively improves the purity of the top product. The use of plate-filled mixing technology effectively improves the mass transfer and separation efficiency of the distillation tower, effectively improves the mass transfer process, and reduces separation energy consumption and costs.

[0054] In one embodiment, it further includes:

[0055] Collect real-time data of the top temperature T1, bottom temperature T2, feed flow F and top output D of the high-efficiency distillation tower;

[0056] According to the deviation ΔT1 between the tower top temperature T1 and the preset target temperature T1_set, a refrigerant flow adjustment signal is generated through PID calculation to adjust the opening of the refrigerant inlet valve of the gravity reflux condenser;

[0057] According to the deviation ΔT2 between the tower bottom temperature T2 and the preset target temperature T2_set, a heat medium flow adjustment signal is generated through PI calculation to adjust the opening of the heat medium inlet valve of the tower bottom reboiler.

[0058] In one embodiment, it further includes:

[0059] Calculate the temperature field distribution inside the tower based on the heat transfer equation:

[0060]

[0061] The light component concentration at the top of the tower is calculated based on the component transfer equation:

[0062]

[0063] Based on the calculation results of the heat transfer equation and the component transfer equation, the state equation ρ = f(p, D, T) is simultaneously established to optimize the overhead extraction volume D and the reboiler heat load Q in real time, and send control instructions to the overhead extraction valve and reflux valve;

[0064] Where ρ is density, T is temperature, and p is pressure. is the gas phase velocity vector in the tower, k is the thermal conductivity of the gas phase in the tower, C p is the relative heat capacity of gas, S T is the heat load input of the bottom reboiler, C s is the volume concentration of the light component s, ρC s is the mass concentration of the light component s, D s is the diffusion coefficient of the light component s, S s is the input amount of light component s in the raw material.

[0065] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. An energy-saving gravity condensation reflux high-efficiency distillation system, characterized in that: include: Buffer tank (1), feed pump (2), feed and discharge thermal coupling heat exchanger (3), high-efficiency distillation tower (4), gravity reflux condenser (5), tower bottom reboiler (6) and tower bottom extraction pump (7); The gravity reflux condenser (5) is arranged at the top of the high-efficiency distillation tower (4) and is in communication with the high-efficiency distillation tower (4); the feed and discharge heat coupling heat exchanger (3) is connected between the buffer tank (1) and the feed inlet of the high-efficiency distillation tower (4); the bottom outlet of the high-efficiency distillation tower (4) is connected to the inlet of the bottom reboiler (6) and the bottom extraction pump (7); and the outlet of the bottom reboiler (6) is connected to the circulation feed inlet of the high-efficiency distillation tower (4); The gravity reflux condenser (5) is used to condense the gas phase at the top of the tower into liquid, and reflux it to the high-efficiency distillation tower (4) by gravity; the inlet and outlet heat coupling heat exchanger (3) is used to exchange heat between the raw materials output from the buffer tank (1) and the bottom product of the high-efficiency distillation tower (4); and the bottom extraction pump (7) is used to output the bottom product.

2. The energy-saving gravity condensation reflux high-efficiency distillation system according to claim 1, characterized in that: The cold side inlet of the inlet and outlet thermal coupling heat exchanger (3) is connected to the output end of the buffer tank (1), the cold side outlet is connected to the feed port of the high-efficiency distillation tower (4), the hot side inlet is connected to the outlet of the tower bottom extraction pump (7), and the hot side outlet is used to connect to the purified water system.

3. The energy-saving gravity condensation reflux high-efficiency distillation system according to claim 1, characterized in that: The cold side inlet of the tower bottom reboiler (6) is connected to the tower bottom outlet of the tower bottom extraction pump (7), and the cold side outlet is connected to the circulation feed port of the high-efficiency distillation tower (4). The heat source of the tower bottom reboiler (6) is high-temperature steam input from the outside.

4. The energy-saving gravity condensation reflux high-efficiency distillation system according to claim 1, characterized in that: The gravity reflux condenser (5) is a partition-type heat exchanger, the refrigerant inlet and outlet of the gravity reflux condenser (5) are respectively connected to an external cold source, and the condensate outlet of the gravity reflux condenser (5) is connected to the top liquid phase distributor or the first tower plate of the high-efficiency distillation tower (4).

5. The energy-saving gravity condensation reflux high-efficiency distillation system according to claim 1, characterized in that: The packing type of the high-efficiency distillation tower (4) is at least one of a tray, a structured packing or a random packing.

6. The energy-saving gravity condensation reflux high-efficiency distillation system according to claim 1, characterized in that: The high-efficiency distillation tower (4) uses the following formula to dynamically adjust the heat load: Q = f(F, η, n, T); Where F is the feed flow rate, η is the packing efficiency, n is the number of theoretical plates, and T is the temperature.

7. A control method for an energy-saving gravity condensation reflux high-efficiency distillation system according to any one of claims 1 to 6, characterized in that: include: After being buffered in the buffer tank, the raw materials are pressurized by the feed pump, and then enter the high-efficiency distillation tower after heat exchange with the bottom product through the inlet and outlet heat coupling heat exchanger; The gas phase at the top of the tower enters the gravity reflux condenser for partial condensation, and the condensate flows back to the top of the tower by gravity, and the uncondensed gas phase is extracted as the top product; The reboiler at the bottom of the tower heats the liquid in the tower kettle to generate rising steam, which participates in distillation. The bottom product is transported to the inlet and outlet thermal coupling heat exchanger through the bottom extraction pump and then discharged after heat exchange.

8. The control method according to claim 7, wherein: Also includes: The tower top temperature, tower bottom temperature, raw material flow and composition data are collected in real time, and the refrigerant flow, heat medium flow, tower top extraction valve and reflux valve opening are dynamically adjusted to enable the system to operate with the lowest energy consumption while meeting the separation conditions.

9. The control method according to claim 7, wherein: Also includes: Collect real-time data of the top temperature T1, bottom temperature T2, feed flow F and top output D of the high-efficiency distillation tower; According to the deviation ΔT1 between the tower top temperature T1 and the preset target temperature T1_set, a refrigerant flow adjustment signal is generated through PID calculation to adjust the opening of the refrigerant inlet valve of the gravity reflux condenser; According to the deviation ΔT2 between the tower bottom temperature T2 and the preset target temperature T2_set, a heat medium flow adjustment signal is generated through PI calculation to adjust the opening of the heat medium inlet valve of the tower bottom reboiler.

10. The control method according to claim 7, wherein: Also includes: Calculate the temperature field distribution inside the tower based on the heat transfer equation: The light component concentration at the top of the tower is calculated based on the component transfer equation: Based on the calculation results of the heat transfer equation and the component transfer equation, the state equation ρ = f(p, D, T) is simultaneously established to optimize the overhead extraction volume D and the reboiler heat load Q in real time, and send control instructions to the overhead extraction valve and reflux valve; Where ρ is density, T is temperature, and p is pressure. is the gas phase velocity vector in the tower, k is the thermal conductivity of the gas phase in the tower, C p is the relative heat capacity of gas, S T is the heat load input of the bottom reboiler, C s is the volume concentration of the light component s, ρC s is the mass concentration of the light component s, D s is the diffusion coefficient of the light component s, S s is the input amount of light component s in the raw material.

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