Double-effect heat pump rectification system

Abstract

The invention belongs to the technical field of heat pump rectification, and particularly relates to a double-effect heat pump rectification system which comprises a first-effect rectification tower feeding pump connected with a preheater, the preheater is connected with a first-effect rectification tower, the first-effect rectification tower is connected with a gas-liquid separator through a screw compressor, and the gas-liquid separator is connected with a tail gas condenser through a second-effect falling film reboiler. The second-effect falling film reboiler is connected with a first-effect reflux discharge pump through a first-effect reflux tank, and the first-effect reflux discharge pump is connected with the preheater; the first-effect rectifying tower is respectively connected with a first-effect falling film reboiler and a first-effect falling film circulating pump; the first-effect rectifying tower is connected with a second-effect rectifying tower through a first-effect tower kettle discharging pump; the first-effect falling film reboiler is connected with a second-effect reflux discharge pump through a second-effect reflux tank; the second-effect falling film reboiler is connected with a second-effect falling film circulating pump and a second-effect rectifying tower, the second-effect falling film reboiler is connected with a second-effect rectifying tower kettle discharging pump through the second-effect rectifying tower, and the second-effect rectifying tower is connected with the first-effect falling film reboiler. According to the invention, double-effect rectification and heat pump rectification are successfully combined, and the cost is low.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of heat pump rectification, and particularly relates to a double-effect heat pump rectification system. BACKGROUND

[0002] Heat pump rectification is a technology that recovers waste heat in the rectification process by integrating a heat pump system, aiming to significantly reduce energy consumption and operating costs. Its core principle is to use a compressor to pressurize and heat the overhead vapor or intermediate heat, and re-input it into the rectification tower as a heat source, thereby reducing the consumption of external steam or electric heating.

[0003] Double-effect rectification is a technology that significantly improves the energy efficiency of a rectification system through energy integration and thermal coupling. Its core lies in the coordinated operation of two or more rectification towers to achieve step-by-step utilization of heat and reduce external energy consumption.

[0004] Double-effect rectification does not have the energy-saving advantages of heat pump rectification. In conventional heat pump rectification processes, one-tower heat pump rectification has the problems of large compressor air volume, high compressor operating cost, and high equipment investment. Heat pump rectification using two compressors in two effects has the problems of large compressor air volume, multiple compressors, and high equipment investment. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a double-effect heat pump rectification system.

[0006] A double-effect heat pump rectification system, characterized in that it comprises an one-effect rectification tower feed pump, which delivers raw materials into a preheater, the preheater is connected to an one-effect rectification tower, the one-effect rectification tower is connected to a gas-liquid separator through a screw compressor, the gas-liquid separator is connected to a tail gas condenser through a two-effect falling film reboiler, the two-effect falling film reboiler is connected to an one-effect reflux tank through an one-effect reflux discharge pump, and the one-effect reflux discharge pump is connected to the preheater. The one-effect rectification tower is connected to an one-effect falling film reboiler and an one-effect falling film circulating pump, respectively, and the one-effect falling film circulating pump is connected to the one-effect falling film reboiler. The one-effect rectification tower is connected to a two-effect rectification tower through an one-effect tower discharge pump, and the two-effect rectification tower is connected to a tail gas condenser through an one-effect falling film reboiler. The one-effect falling film reboiler is connected to a two-effect reflux tank through a two-effect reflux discharge pump. The two-effect falling film reboiler is connected to a two-effect falling film circulating pump, which is connected to a two-effect rectification tower. The two-effect falling film reboiler is connected to a two-effect rectification tower through a two-effect rectification tower discharge pump, and the two-effect rectification tower is connected to an one-effect falling film reboiler.

[0007] It should be noted that, compared with the conventional heat pump rectification system using two compressors in two effects, the present application only needs one single compressor (screw compressor) to achieve better energy-saving effect.

[0008] Preferably, the first reflux tank is connected to the hot side inlet of the preheater through a first reflux discharge pump, and the hot side outlet of the preheater is connected to the reflux port of the first rectifying tower for reflux.

[0009] Preferably, the preheater is connected to a product cooler for cooling and producing products.

[0010] Preferably, the second reflux discharge pump is connected to the second rectifying tower for reflux.

[0011] Preferably, the second reflux discharge pump is connected to a product cooler for cooling and producing products.

[0012] Preferably, the second rectifying tower kettle discharge pump is connected to a reboiling cooler for waste water treatment.

[0013] Preferably, the first rectifying tower is connected to a start-up reboiler.

[0014] Preferably, the start-up reboiler is connected to an external low-pressure steam, and the low pressure is > 0.2 MPaG, and the start-up reboiler discharges steam condensate.

[0015] Preferably, the raw materials or products include at least one of methanol, ethanol, chloroform, acetone, and ethyl acetate.

[0016] It should be noted that by using the foregoing technical solutions, the overhead gas of the second rectifying tower is coupled to the first falling film reboiler of the first rectifying tower, and the overhead gas of the first rectifying tower is pressurized by a screw compressor and then coupled to the second falling film reboiler of the second rectifying tower, thereby successfully realizing a double-effect heat coupling system of a rectifying tower combined with heat pump technology.

[0017] Preferably, taking methanol rectification as an example, under the conditions of 96% methanol feed, 99% methanol product, and 1% methanol content in waste water, the bottom temperature of the first rectifying tower is 70℃, the overhead temperature of the first rectifying tower is 65.5℃, the reflux ratio of the first rectifying tower is 0.27, the bottom temperature of the second rectifying tower is 109℃, the overhead temperature of the second rectifying tower is 80℃, and the reflux ratio of the second rectifying tower is 0.81; the overhead operating pressure of the first rectifying tower is 103 kPa, and the overhead operating pressure of the second rectifying tower is 180 kPa.

[0018] It should be noted that, by adopting the technical scheme, the present application utilizes the characteristics that the boiling point of the first section of the column before concentration is low, and the boiling point of the second section of the column during concentration is high, splits the rectifying column into two effects, uses two columns (a one-effect rectifying column and a two-effect rectifying column), the boiling point of the column bottom of the one-effect rectifying column is close to the boiling point of the column top, and the heating difficulty of the two-effect rectifying column is relatively low, the one-effect rectifying column top product waste heat is compressed by a compressor, the two column temperature rises are overcome, and the one-effect rectifying column top is directly heated by the two-effect rectifying column bottom, and then the two-effect rectifying column top is heated by the one-effect rectifying column, and the different reflux ratios of the two columns are also considered in the process.

[0019] Many technical difficulties are faced in the technical scheme design process, for example, when the ratio of the one-effect rectifying column and the two-effect rectifying column is considered, the air volume (including the column top gas of the two parts of the discharge and the reflux) and the temperature rise (the boiling point difference between the column top and the column bottom) of the compressor need to meet the total demand of the two-effect rectifying column as much as possible, and the tail gas part basically has no surplus amount, and under such conditions, the technical scheme of the present application is essentially different from the conventional double-effect rectifying technology with an external heat source.

[0020] Furthermore, the conventional double-effect process must use an external heat source, the second-effect column top needs to be cooled by an external cold source, and the use of steam cannot be fundamentally reduced.

[0021] The system of the present application has the functions of heat coupling of the operating temperatures of the two columns and heat recovery of the two columns, the reboilers of the two columns are all heat coupled, the one-effect rectifying column is double-effect heat coupled, and the two-effect rectifying column is heat pump heat coupled, the excess steam of the two columns is combined and sent to a tail gas condenser, the steam consumption is reduced, the cooling water consumption is reduced, and compared with the conventional heat pump rectifying system and the double-effect rectifying system, great improvement is achieved.

[0022] The present application has the following beneficial effects: The double-effect heat pump rectifying system of the present application has the advantages of energy saving of the heat pump rectifying and heat coupling of the double-effect rectifying column, the column top steam of the one-effect rectifying column is pressurized by a compressor to heat the column bottom of the two-effect rectifying column, the column top steam of the two-effect rectifying column is operated under pressure to heat the column bottom of the one-effect rectifying column, the number and air volume of the compressors are reduced, the operation cost is saved, the equipment investment cost is saved, the core equipment of the system is avoided from being connected in series, and the stability is stronger.

[0023] The double-effect heat pump rectifying system of the present application can realize the following effects: 1. Heat recovery is sufficient: preheating of the feed, heat recovery of the column top of the one-effect rectifying column, and heat recovery of the column top of the two-effect rectifying column.

[0024] 2. Small compressor gas volume: the double-effect process of the double-effect rectifying tower greatly reduces the gas volume, because the screw compressor only processes the overhead vapor of the primary rectifying tower, and the heat of the overhead vapor of the primary rectifying tower generates the overhead vapor of the primary rectifying tower, which is efficiently reused as heat supply for the reboiler of the secondary rectifying tower, so that the gas volume of the compressor is reduced by about one half.

[0025] 3. Lower energy consumption: the double-effect process of the double-effect rectifying tower reduces the power of the compressor, and the technology is mature, the degree of automation is high, and the equipment selection is reasonable. More specifically, in the double-effect rectifying tower, the concentration of the primary rectifying tower is high, the boiling point of the tower is close to the boiling point of the overhead product, and under the premise of reducing the gas volume by half, the pressure ratio of the compressor increases from 5 to 5.8 (taking methanol as an example), and the energy consumption of the system is also lower. Compared with the single-effect heat pump rectification, the double-effect heat pump rectification system can save about 30-40% of energy.

[0026] 4. Less investment or lower cost: because the cost of the compressor is related to the gas volume and the motor power of the compressor, the larger the gas volume, the higher the investment, and the more the number of compressors, the higher the investment. The gas volume of the compressor is small, the compressor gas volume is only half of the conventional single-effect heat pump rectification, and the number of compressors is 1, which greatly reduces the cost.

[0027] 5. Strong controllability: the auxiliary heating of the start-up reboiler can respond to the working condition fluctuation, the screw compressor has strong load regulation capability, and the tail gas condenser ensures the outlet temperature.

[0028] 6. More stable system: the double-effect heat pump rectification system of the present application only relies on one compressor (screw compressor), the number of core equipment is small, the failure rate is low, and the system is more stable.

[0029] 7. Reasonable thermal coupling design: the overhead gas of the secondary rectifying tower is coupled with the tower bottom of the primary rectifying tower, and the overhead gas heat pump of the primary rectifying tower is coupled with the tower bottom of the secondary rectifying tower.

[0030] 8. Subsequent treatment: the outlet of the secondary rectifying tower can be divided into several cases, generally, the outlet of the secondary rectifying tower is connected with the reboiling cooler, and the reboiling cooler sends the reboiling material out of the rectification system, or the outlet of the secondary rectifying tower is connected with the next stage of the rectifying tower, and the material is further separated.

[0031] In summary, the present application successfully improves the heat pump rectification system, combines with the double-effect rectification, forms a unique heat pump double-effect rectification system, and only needs one compressor. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation of the present application.

[0033] In the drawings: Figure 1 is a schematic diagram of the preparation process of the present application.

[0034] marked in the figure: 1, product cooler; 2, one-effect rectification tower feed pump; 3, start-up reboiler; 4, one-effect rectification tower; 5, one-effect falling film reboiler; 6, preheater; 7, one-effect falling film circulating pump; 8, two-effect reflux tank; 9, two-effect reflux discharge pump; 10, one-effect tower kettle discharge pump; 11, one-effect reflux discharge pump; 12, screw compressor; 13, gas-liquid separator; 14, one-effect reflux tank; 15, two-effect falling film circulating pump; 16, two-effect falling film reboiler; 17, two-effect rectification tower; 18, tail gas condenser; 19, reboiling cooler; 20, two-effect rectification tower kettle discharge pump. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0036] Embodiment 1 A two-effect heat pump rectification system comprises a one-effect rectification feed unit, a one-effect rectification tower rectification unit, a one-effect rectification tower distillation unit, a two-effect rectification tower feed unit, a two-effect rectification tower rectification unit, and a two-effect rectification tower distillation unit. In order to more clearly describe the functions of each part or device, the connection relationship is described in different units.

[0037] The one-effect rectification tower feed unit: the outlet of the raw material tank is connected to the inlet of the one-effect rectification tower feed pump 2, the outlet of the one-effect rectification tower feed pump 2 is connected to the inlet of the cold side of the preheater 6, and the outlet of the cold side of the preheater 6 is connected to the inlet of the one-effect rectification tower 4.

[0038] The vapor outlet of the one-effect rectification tower 4 is connected with the inlet of the screw compressor 12, the outlet of the screw compressor 12 is connected with the inlet of the gas-liquid separator 13, the outlet of the gas-liquid separator 13 is connected with the inlet of the shell side of the two-effect falling film reboiler 16, the tail gas outlet of the shell side of the two-effect falling film reboiler 16 is connected with the tail gas condenser 18, the condensate outlet of the shell side of the two-effect falling film reboiler 16 is connected with the inlet of the one-effect reflux tank 14, a gas phase balance pipeline is arranged between the two-effect falling film reboiler 16 and the one-effect reflux tank 14 to avoid the influence of the pressure difference between the two devices on the liquid discharge. The outlet of the one-effect reflux tank 14 is connected with the inlet of the one-effect reflux discharge pump 11, and the outlet of the one-effect reflux discharge pump 11 is connected with the hot side inlet of the preheater 6. The hot side outlet of the preheater 6 is divided into two connection routes, one route is that the hot side outlet of the preheater 6 is connected with the reflux port of the one-effect rectification tower 4 to complete the reflux of the one-effect rectification tower, and the other route is that the hot side outlet of the preheater 6 is connected with the hot side inlet of the product cooler 1, and the outlet of the product cooler 1 is connected with an external product storage unit to store the methanol product.

[0039] The one-effect rectification tower distillation unit: in the distillation stage of the one-effect rectification tower 4, the liquid phase material provided by the reflux and the feed flows from top to bottom through each stage of the tray and carries out gas-liquid mass transfer with the rising vapor. In this process, the low-boiling-point components in the liquid phase are continuously stripped, and the concentration gradually decreases, and finally the product rich in high-boiling-point components is obtained in the tower kettle, thereby completing the distillation of the low-boiling-point components.

[0040] The reflux and the feed of the one-effect rectification tower 4 gradually reduce through the gas-liquid mass transfer of each stage of the tray to complete the distillation of the low-boiling-point components in the tower kettle of the one-effect rectification tower 4. Specifically, the liquid outlet at the bottom of the one-effect rectification tower 4 is connected with the liquid inlet of the tube side of the start-up reboiler 3, the outlet of the tube side of the start-up reboiler 3 is connected with the gas-liquid inlet of the tower kettle of the one-effect rectification tower 4. The low-pressure steam supplied externally is connected with the inlet of the shell side of the start-up reboiler 3, and the condensed water at the outlet of the shell side of the start-up reboiler 3 is sent to the outside through a drain valve to realize the discharge of the steam condensate. The liquid outlet at the bottom of the one-effect rectification tower 4 is connected with the inlet of the one-effect falling film circulating pump 7, the outlet of the one-effect falling film circulating pump 7 is connected with the feed inlet at the top of the tube side of the one-effect falling film reboiler 5, and the outlet of the tube side of the one-effect falling film reboiler 5 is connected with the gas-liquid inlet of the tower kettle of the one-effect rectification tower 4. The liquid outlet of the tower kettle of the one-effect rectification tower 4 is connected with the inlet of the one-effect kettle discharge pump 10 to complete the one-effect rectification tower distillation unit.

[0041] The two-effect rectification tower feed unit: the outlet of the one-effect kettle discharge pump 10 is connected with the inlet of the middle part of the two-effect rectification tower 17 to complete the two-effect rectification feed.

[0042] The two-effect rectification column distillation unit: in the stripping stage of the two-effect rectification column 17, the liquid phase material provided by the reflux and the feed flows from top to bottom through each stage of the tray, and gas-liquid mass transfer is carried out with the rising steam. In this process, the low-boiling-point components in the liquid phase are continuously stripped, and the concentration gradually decreases, and finally the product rich in high-boiling-point components is obtained in the tower kettle, so that the stripping of low-boiling substances is completed. Specifically, the two-effect rectification column 17 tower kettle discharge port is connected with the inlet of the two-effect falling film circulation pump 15, the outlet of the two-effect falling film circulation pump 15 is connected with the top tube passage feed port of the two-effect falling film reboiler 16, and the tube passage discharge port of the two-effect falling film reboiler 16 is connected with the tower kettle gas-liquid inlet of the two-effect rectification column 17, to complete the reboiler process. The two-effect rectification column 17 tower kettle liquid discharge port is connected with the inlet of the two-effect rectification column kettle discharge pump 20, to complete the two-effect rectification column stripping unit.

[0043] The two-effect rectification column distillation unit: in the stripping stage of the two-effect rectification column 17, the liquid phase material provided by the reflux and the feed flows from top to bottom through each stage of the tray, and gas-liquid mass transfer is carried out with the rising steam. In this process, the low-boiling-point components in the liquid phase are continuously stripped, and the concentration gradually decreases, and finally the product rich in high-boiling-point components is obtained in the tower kettle, so that the stripping of low-boiling substances is completed. Specifically, the two-effect rectification column 17 tower kettle discharge port is connected with the inlet of the two-effect falling film circulation pump 15, the outlet of the two-effect falling film circulation pump 15 is connected with the top tube passage feed port of the two-effect falling film reboiler 16, and the tube passage discharge port of the two-effect falling film reboiler 16 is connected with the tower kettle gas-liquid inlet of the two-effect rectification column 17, to complete the reboiler process. The two-effect rectification column 17 tower kettle liquid discharge port is connected with the inlet of the two-effect rectification column kettle discharge pump 20, to complete the two-effect rectification column stripping unit.

[0044] The two-effect rectification column tower kettle discharge and subsequent treatment: the two-effect rectification column 17 tower kettle discharge can be divided into various cases, and in general cases, the outlet of the two-effect rectification column kettle discharge pump 20 is connected with the hot side inlet of the reboiling cooler 19, and the reboiling cooler 19 is connected with the two-effect rectification column kettle discharge pump 20. The reboiling cooler 19 hot side outlet reboiling material is sent out of the rectification system, and in some cases, the outlet of the two-effect rectification column kettle discharge pump 20 is connected with the feed port of the next stage rectification column, and the material is continuously separated by rectification.

[0045] The working process of the two-effect heat pump rectification system is as follows: the feed is preheated by the hot material, enters the one-effect rectification column 4, the one-effect rectification column 4 tower top steam is pressurized by the screw compressor 12, and is used to heat the two-effect rectification column 17 tower kettle, the one-effect rectification column 4 tower kettle discharge enters the two-effect rectification column 17. The operating pressure of the two-effect rectification column 17 tower top is increased, the two-effect rectification column 17 tower top steam is used to heat the one-effect rectification column 4 tower kettle, and the two-effect rectification column 17 tower kettle discharge is cooled by the product cooler 1 and then sent out of the system. The tower top steam condensate of each column is quantitatively refluxed to the top of each column, and the tower top discharge is combined and sent to the product cooler 1.

[0046] Example 2 The working process is more specific in this example than in Example 1, and is as follows: The working process of the double-effect heat pump rectification system is as follows: the material is stored in the raw material tank, the material is pumped from the raw material tank through the feed pump 2 of the primary rectification tower to the cold side of the preheater 6, in the preheater 6, the relatively low-temperature material exchanges heat with the high-temperature reflux liquid or product liquid from the top of the primary rectification tower 4, which runs through the hot side of the preheater 6, and the material is preheated to near the temperature of the feed plate of the primary rectification tower 4, thus completing the preheating. The preheated material flows out of the cold side outlet of the preheater 6 and enters the middle feed port of the primary rectification tower 4.

[0047] 1. Processing of the primary rectification tower 4 Rectification: the preheated material flows downward in the primary rectification tower 4, and countercurrently exchanges heat and mass with the rising vapor in the tray. The volatile components (such as methanol) continuously vaporize into the rising vapor, and the non-volatile components (such as water) continuously condense into the downward liquid. The rising vapor reaches the top of the primary rectification tower 4 and becomes superheated or saturated vapor rich in volatile components (target product).

[0048] Distillation: the concentration of non-volatile components in the downward liquid becomes higher and higher. The liquid reaches the bottom of the primary rectification tower 4, is pumped out by the primary falling film circulating pump 7, and after being pressurized, is sent to the top of the tube side of the primary falling film reboiler 5. In the primary falling film reboiler 5, the tower bottom liquid in the tube side flows down along the tube wall in the form of a falling film.

[0049] The vapor rich in volatile components at the top of the primary rectification tower 4 leaves the top of the primary rectification tower 4 and enters the screw compressor 12. The screw compressor 12 compresses and pressurizes the vapor, increasing its pressure and saturation temperature. The compressed high-temperature and high-pressure vapor enters the gas-liquid separator 13. Here, a small amount of entrained liquid droplets or condensate that may be generated during compression is separated out, mainly to prevent liquid from entering subsequent equipment and affecting the equipment and process.

[0050] The high-temperature and high-pressure vapor after separation, still mainly in the gas phase, enters the shell side of the secondary falling film reboiler 16. In the shell side of the secondary falling film reboiler 16, the high-temperature and high-pressure vapor condenses, releasing a large amount of latent heat of condensation. This part of the heat is used to heat the tower bottom liquid of the secondary rectification tower 17 flowing in the tube side of the secondary falling film reboiler 16.

[0051] The condensed liquid (mainly the product component at the top of the primary rectification tower 4) flows out from the condensate outlet of the shell side of the secondary falling film reboiler 16 and enters the primary reflux tank 14.

[0052] The product and reflux from the first rectifier column 4 is the condensate from the shell side of the second falling film reboiler 16, which is drawn into the first reflux drum 14. This condensate is highly pure, as it is the condensate of the overhead vapor from the first rectifier column 4 after compression. The condensate is buffered and stored in the first reflux drum 14. The first reflux pump 11 draws the condensate from the first reflux drum 14 and sends it to the hot side of the preheater 6 after pressurization.

[0053] At the hot side of the preheater 6, the high temperature reflux condensate transfers heat to the feed liquid at the cold side to preheat the feed liquid and cool itself. The cooled liquid is divided into two streams at the outlet of the hot side of the preheater 6: Reflux liquid: returned to the overhead reflux port of the first rectifier column 4 to provide internal reflux, control the purity of the overhead product, and control the liquid to vapor ratio in the rectifying section.

[0054] Product liquid: sent to the hot side of the product cooler 1, further cooled to the storage temperature, and then sent out of the system as the product of the first rectifier column 4 for storage, such as the methanol product.

[0055] The column sump liquid of the first rectifier column 4 is heated by the overhead vapor of the second rectifier column 17 in the tube side of the first falling film reboiler 5, partially vaporized, and forms a gas-liquid mixture. More details are described in the following.

[0056] The gas-liquid mixture is returned to the gas-liquid inlet of the column sump of the first rectifier column 4 from the outlet of the tube side of the first falling film reboiler 5 to provide the rising vapor for the first rectifier column 4.

[0057] Part of the column sump liquid in the first rectifier column 4 (rich in difficultly volatile components) is drawn out by the first column sump pump 10 as the feed for the second rectifier column 17.

[0058] The liquid drawn out by the first column sump pump 10 is introduced into the middle feed port of the second rectifier column 17.

[0059] 2. Treatment of the second rectifier column 17 Rectification: The feed liquid flows downward in the second rectifier column 17 and countercurrently contacts and mass transfers with the rising vapor from the bottom of the second rectifier column 17 on the trays. The remaining volatile components in the feed liquid are further purified into the rising vapor. The rising vapor reaches the top of the column and becomes a vapor rich in volatile components (target product). The pressure is usually higher than the pressure at the top of the first rectifier column 4, and the temperature at the top of the second rectifier column 17 is higher than the temperature at the column sump of the first rectifier column 4.

[0060] Distillation: The concentration of difficultly volatile components in the downward flowing liquid continues to increase. The liquid reaches the column sump of the second rectifier column 17 and is drawn out by the second falling film circulation pump 15 and sent to the top of the tube side of the second falling film reboiler 16 after pressurization. In the second falling film reboiler 16, the column sump liquid in the tube side flows down the tube wall in the form of a falling film.

[0061] The aforementioned "high pressure steam, still in gas phase, after separation, enters the shell side of the second effect falling film reboiler 16. In the shell side of the second effect falling film reboiler 16, the high pressure steam condenses, releasing a large amount of latent heat of condensation. This amount of heat is used to heat the second effect column 17 column liquid flowing in the tube side of the second effect falling film reboiler 16". In more detail, these high pressure steam from the top of the first effect column 4, after separation in the gas-liquid separator 13, condenses in the shell side of the second effect falling film reboiler 16, releasing heat. This amount of heat is absorbed by the second effect column 17 column liquid flowing in the tube side of the second effect falling film reboiler 16, partially vaporizing it, forming a gas-liquid mixture.

[0062] This gas-liquid mixture returns from the tube side outlet of the second effect falling film reboiler 16 to the gas-liquid inlet of the second effect column 17 column, providing the column with rising vapor. The final column residue (rich in the most difficult to vaporize components) from the second effect column 17 column is pumped out by the second effect column discharge pump 20.

[0063] The aforementioned "the first effect column 4 column liquid is heated in the tube side of the first effect falling film reboiler 5 by the shell side second effect column top vapor, partially vaporizing it, forming a gas-liquid mixture". In more detail, the second effect column 17 column top vapor leaves the column top and enters the shell side of the first effect falling film reboiler 5. In the shell side of the first effect falling film reboiler 5, the second effect column 17 column top vapor condenses, releasing latent heat of condensation. This amount of heat is used to heat the first effect column 4 column liquid flowing in the tube side of the first effect falling film reboiler 5, providing it with reboiling heat.

[0064] The condensed liquid from the second effect column 17 (mainly the second effect column 17 column top product components) flows out from the shell side condensate outlet of the first effect falling film reboiler 5 into the second effect reflux drum 8. The first effect falling film reboiler 5 shell side tail gas (non-condensable gas) enters the tail gas condenser 18 for further treatment.

[0065] Second effect column 17 product and reflux: The liquid from the shell side condensate of the first effect reboiler 5, entering the second effect reflux drum 8, is the condensate of the second effect column 17 column top vapor. This liquid is buffered and stored in the second effect reflux drum 8.

[0066] The second effect reflux pump 9 pumps the liquid from the second effect reflux drum 8, pressurizing it. The pressurized liquid is divided into two streams: Reflux liquid: returns to the second effect column 17 column top reflux inlet, providing internal reflux.

[0067] Product liquid: enters the hot side of the product cooler 1, can be combined with or in parallel with the first effect column 4 product liquid, is cooled to storage temperature, and then sent out of the system as the product of the second effect column 17, such as the methanol product.

[0068] Second effect column 17 residue treatment: The final column residue (mainly difficult to vaporize components such as water, heavy components, and impurities) from the second effect column 17 column is pumped out by the second effect column discharge pump 20.

[0069] The residual liquid is extracted and enters the hot side of the reboiler cooler 19 for cooling, and is discharged from the system or enters the subsequent rectification equipment after reaching the discharge or storage temperature.

[0070] 3. Treatment of the remaining auxiliary systems Startup reboiler 3: used during the system startup phase or when the heat supplied by the second-effect rectification tower 17 is insufficient. External low-pressure steam enters the shell side of the startup reboiler 3, heating the liquid from the first-effect rectification tower 4 in the tube side, and providing a startup heat source or supplemental heat for the first-effect rectification tower 4. It is usually closed or used as a backup after normal operation. The steam condensate is discharged through the trap of the startup reboiler 3.

[0071] Tail gas condenser 18: receives the tail gas (non-condensable gas) from the shell side of the first-effect falling film reboiler 5 and the shell side of the second-effect falling film reboiler 16, condenses and cools it, separates a small amount of liquid components that may be entrained, and discharges the non-condensable gas from the system into the tail gas treatment unit.

[0072] Example 3 In this example, specific parameters during operation are given, as follows: When the material is methanol, a methanol solution with a temperature of 30°C, atmospheric pressure, a concentration of 96%, and a flow rate of 21 t / h is selected from the raw material tank and enters the first-effect rectification tower through the feed pump 2. After preheating by the preheater 6, the methanol solution is heated to 68°C and enters the first-effect rectification tower 4 at the feed inlet. The bottom temperature of the first-effect rectification tower 4 is 70°C, and the top temperature is 65.5°C. The reflux ratio of the first-effect rectification tower 4 is 0.27, and the concentration of the methanol outflow is 92%. The outflow from the first-effect rectification tower 4 at 70°C enters the second-effect rectification tower 17 at the feed inlet. The bottom temperature of the second-effect rectification tower 17 is 109°C, and the top temperature is 80°C. The reflux ratio of the second-effect rectification tower 17 is 0.81, and the concentration of the methanol outflow is 1%. The purity of the methanol product from the first-effect rectification tower 4 is 99.54%, and the purity of the methanol product from the top of the second-effect rectification tower 17 is 99.56%. The operating pressure at the top of the first-effect rectification tower 4 is 103 kPa, and the temperature is raised to 51°C by the screw compressor 12, which serves as the heat source for the second-effect falling film reboiler 16. The operating pressure at the top of the second-effect rectification tower 17 is 180 kPa, which serves as the heat source for the first-effect falling film reboiler 5.

[0073] Temperature gradient requirement: To ensure the efficiency of heat transfer, the operating pressure of the first tower should be maintained at a temperature 8-10°C higher than the boiling point of the liquid at the bottom of the second tower. This temperature difference is the key to heat coupling.

[0074] The inlet pressure of the compressor is 105 kPaA, corresponding to a saturated temperature of 66°C, and the outlet pressure is 600 kPaA, corresponding to a saturated temperature of 117°C.

[0075] It should be noted that in addition to methanol, the material can also be ethanol, chloroform, acetone and ethyl acetate, and the double-effect heat pump rectification system of the application can be widely applied in the rectification and purification process of methanol, ethanol, chloroform, acetone and ethyl acetate and other materials.

[0076] It should be further explained that the meanings and principles of the terms used in the application are understood and known by those skilled in the art.

[0077] The reflux ratio is the ratio of the reflux liquid flow rate to the top product flow rate.

[0078] The screw compressor 12 is based on the double-screw volumetric compression principle, and realizes the suction, compression and discharge of the gas through a pair of intermeshing helical male and female rotors.

[0079] The above only describes the preferred embodiments of the application and is not intended to limit the application. Although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A double-effect heat pump rectification system, characterized by, The one-effect rectification tower feed pump transports raw materials into the preheater, the preheater is connected with the one-effect rectification tower, the one-effect rectification tower is connected with the gas-liquid separator through the screw compressor, the gas-liquid separator is connected with the tail gas condenser through the two-effect falling film reboiler, the two-effect falling film reboiler is connected with the one-effect reflux tank through the one-effect reflux discharge pump, and the one-effect reflux discharge pump is connected with the preheater; The one-effect rectification tower is connected with the one-effect falling film reboiler and the one-effect falling film circulating pump, the one-effect falling film circulating pump is connected with the one-effect falling film reboiler; the one-effect rectification tower is connected with the two-effect rectification tower through the one-effect tower bottom discharge pump, and the two-effect rectification tower is connected with the tail gas condenser through the one-effect falling film reboiler; the one-effect falling film reboiler is connected with the two-effect reflux tank through the two-effect reflux discharge pump. The two-effect falling film reboiler is connected with the two-effect falling film circulating pump and the two-effect rectification tower, the two-effect falling film reboiler is connected with the two-effect rectification tower bottom discharge pump through the two-effect rectification tower, and the two-effect rectification tower is connected with the one-effect falling film reboiler.

2. A double-effect heat pump rectifying system according to claim 1, characterized in that, The one-effect reflux tank is connected with the preheater through the one-effect reflux discharge pump and the hot side inlet of the preheater, and the hot side outlet of the preheater is connected with the reflux port of the one-effect rectification tower for reflux.

3. The double-effect heat pump rectifying system of claim 1, wherein, The preheater is connected with the product cooler for cooling and producing products.

4. The double-effect heat pump rectifying system of claim 1, wherein, The two-effect reflux discharge pump is connected with the two-effect rectification tower for reflux.

5. The double-effect heat pump rectifying system of claim 1, wherein, The two-effect reflux discharge pump is connected with the product cooler for cooling and producing products.

6. The double-effect heat pump rectifying system of claim 1, wherein, The two-effect rectification tower bottom discharge pump is connected with the reboiling cooler for waste water treatment.

7. The double-effect heat pump rectifying system of claim 1, wherein, The one-effect rectification tower is connected with the start-up reboiler.

8. A double-effect heat pump rectifying system according to claim 7, wherein, The start-up reboiler is connected with external low-pressure steam, the low pressure is >0.2MPaG, and the start-up reboiler discharges steam condensate.

9. The double-effect heat pump rectifying system according to claim 3 or 5, wherein, The raw materials or products include at least one of methanol, ethanol, chloroform, acetone, and ethyl acetate.

10. A double-effect heat pump rectifying system according to any one of claims 1 to 8, characterized in that, Under the conditions of 96% methanol feed, 99% methanol product, and 1% methanol content in waste water, the bottom temperature of the one-effect rectification tower is 70℃, the top temperature of the one-effect rectification tower is 65.5℃, the reflux ratio of the one-effect rectification tower is 0.27, the bottom temperature of the two-effect rectification tower is 109℃, the top temperature of the two-effect rectification tower is 80℃, the reflux ratio of the two-effect rectification tower is 0.81, the top operating pressure of the one-effect rectification tower is 103kPa, and the top operating pressure of the two-effect rectification tower is 180kPa.

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