Energy-saving device and method for pentane rectification by coupling with energy heat pump

Abstract

The application discloses a kind of pentane rectification energy heat pump coupling energy-saving device and method, belong to the energy-saving technical field based on heat pump principle.Pentane rectification heat pump coupling energy-saving method is using pentane rectification column top oil gas directly as heat pump working substance, high temperature oil gas of compressor outlet is used as pentane rectification column bottom reboiler heat source.Under the condition of meeting pentane rectification system production process, pentane rectification and heat pump system cold exchange process are coupled and optimized, process medium process temperature level is reasonably utilized, the temperature difference required by compressor inlet and outlet and heat pump compression ratio are reduced, the heat required by pentane rectification system production process energy is coupled and closed loop, heat pump conversion efficiency (COP) is improved to 6.0 or more, compared with traditional rectification process, energy-saving rate is more than 60%, carbon emission reduction rate is more than 70%.

Description

Technical Field

[0001] This invention relates to a highly efficient energy-saving method for coupling energy (heat and cold) in the pentane distillation process based on the principle of heat pumps, and belongs to the field of heat pump energy-saving technology. Background Technology

[0002] Pentane foaming agents and high-purity pentane products are widely used in insulation, building materials production, and as solvents and desorbents in petrochemical products. Currently, pentane foaming agents and high-purity pentane products are extracted from saturated light naphtha or reformed topping oil components that are lighter than pentane through distillation. The reboiler at the bottom of the pentane distillation column requires a large amount of high-temperature heat to heat the bottom oil to boiling point and evaporate. However, due to the limitations of the second law of thermodynamics, the low-temperature oil and gas heat at the top of the column is difficult to effectively utilize for the high-temperature reboiler at the bottom. Therefore, an external high-temperature heat source is needed for heating the reboiler, and a cooling medium is needed to condense and cool the low-temperature oil and gas at the top of the column.

[0003] Conventional heat pumps typically use externally supplied heat pump working fluid. However, using externally supplied heat pump working fluid in the distillation process poses a risk of leakage between the heat pump working fluid and the process medium, leading to contamination of both. Furthermore, waste heat needs to be recovered through heat pump working fluid exchange with the low-temperature oil and gas at the top of the column, sacrificing the heat exchange temperature and resulting in an increased compression ratio and a lower heat pump efficiency (COP) than 3.0. Additionally, heat pump technology cannot efficiently meet all the energy requirements of the distillation process, necessitating external energy supply. Due to the complexity of the process, its low energy-saving and carbon-reduction properties, and its low economic efficiency, it is difficult to promote its application in the distillation of pentane products. Summary of the Invention

[0004] The technical problem solved by this invention is to propose an energy-efficient, energy-saving, and carbon-reducing device and method for the distillation process of pentane products, which has good economic benefits. Based on the principle of heat pumps, it couples the required cooling and heating energy for the pentane distillation process, achieving a heat pump efficiency (COP) value of over 6.0. Compared with traditional distillation processes, it achieves an energy saving rate of over 60% and a carbon emission reduction rate of over 70%.

[0005] To solve the above-mentioned technical problems, the technical solution proposed in this invention is: a pentane distillation heat pump coupling energy-saving method, wherein the low-pressure / low-temperature pentane oil and gas components at the top of the pentane distillation column are directly used as the working fluid of the heat pump.

[0006] Preferably, it consists of three heat exchangers and one oil-free lubricated insulated compressor integrated into the pentane distillation system process, coupling the heat and cold energy used in pentane distillation.

[0007] Preferably, the oil-free adiabatic compressor in the heat pump process is an oil-free screw compressor, reciprocating compressor, or turbo compressor.

[0008] Preferably, in the heat pump process, one overhead oil-gas heat exchanger is used to exchange heat between the low-pressure / low-temperature oil-gas from the top of the pentane distillation column and the high-pressure / high-temperature liquid phase overhead oil-gas component condensed at the outlet of the reboiler at the bottom of the pentane distillation column; one heat exchanger is used by the reboiler at the bottom of the distillation column to heat the bottom oil of the column from the high-pressure / high-temperature vapor phase overhead oil-gas component at the compressor outlet; and one feed heat exchanger is used to exchange heat between the feed of the pentane distillation column and the high-pressure liquid phase overhead oil-gas component condensed from the overhead oil-gas heat exchanger to recover waste heat.

[0009] Preferably, the compressor uses frequency conversion to adapt to changes in production load, and uses outlet pressure control to adjust the compressor's compression ratio and outlet temperature.

[0010] To solve the above-mentioned technical problems, another technical solution proposed by this invention is: a pentane distillation heat pump coupling energy-saving device, which consists of a pentane distillation column, a top oil-gas heat exchanger, a reflux tank, a bottom reboiler, an oil-free lubricated insulated compressor, a raw material heat exchanger, an oil-free lubricated insulated compressor frequency converter, and a compressor outlet pressure control circuit; it uses metal pipes to connect them into a system to couple the heat and cold energy used in pentane distillation; the top of the pentane distillation column is saturated. The oil and gas first pass through the top oil and gas heat exchanger and the bottom reboiler to condense the high-temperature liquid phase of the top oil and gas, which recovers heat. Then, after being adiabatically compressed and heated by an oilless and lubricated adiabatic compressor, it enters the bottom reboiler of the pentane distillation column as a heat source. After condensing and exchanging heat with the bottom oil, it passes through the top oil and gas heat exchanger and the top oil and gas of the pentane distillation column, and the heat exchanger and the feedstock of the distillation column for heat exchange and cooling before entering the reflux tank. After being collected from the reflux tank, part of it is returned to the pentane distillation column from the top as reflux, and the other part is collected as product.

[0011] Preferably, the oil-free lubricated insulated compressor uses frequency conversion to adapt to changes in production load, and uses outlet pressure control to adjust the compressor's compression ratio and outlet temperature.

[0012] The pentane distillation heat pump coupling energy-saving method of the present invention is as follows:

[0013] 1. The low-pressure (0.08~0.20MPa, saturated phase) / low-temperature oil and gas at the top of the pentane distillation column is directly used as the working fluid of the heat pump. It first passes through the oil and gas heat exchanger at the top of the column and the high-temperature liquid phase oil and gas at the bottom of the column after condensation in the reboiler to recover heat.

[0014] 2. After heat exchange and heating, the oil and gas at the top of the low-pressure pentane distillation column are adiabatically compressed by an oil-free adiabatic compressor (compression ratio 2.0-4.0) and then heated before entering the reboiler at the bottom of the pentane distillation column as a heat source. It first exchanges heat with the bottom oil and then condenses. After that, it passes through the top oil and gas heat exchanger with the low-pressure / low-temperature oil and gas at the top of the pentane distillation column, and the heat exchanger with the feedstock of the distillation column for heat exchange and cooling before entering the reflux tank.

[0015] 3. After condensation and cooling in the reflux tank, part of the liquid oil at the top of the column is returned to the distillation column as reflux, and the other part is collected as product.

[0016] 4. The compressor uses frequency conversion to adapt to changes in production load, and uses outlet pressure control to adjust the compressor's compression ratio and outlet temperature.

[0017] Beneficial effects:

[0018] 1. This pentane distillation heat pump coupling energy-saving method directly uses the low-pressure / low-temperature oil and gas at the top of the column as the heat pump working fluid, which reduces the pollution of materials caused by possible leakage of process media and heat pump working fluid, and reduces the cost of heat pump working fluid. At the same time, because the low-pressure / low-temperature oil and gas at the top of the column is used as the heat pump working fluid, the heat exchange process is simplified, the heat pump temperature utilization efficiency is improved, and it is more conducive to reducing the compression ratio of the compressor and improving the working efficiency of the heat pump.

[0019] 2. The pentane overhead oil and gas is pentane. As a heat pump working fluid, its maximum operating pressure in the pentane distillation heat pump coupling energy-saving process is less than 0.8 MPa, which is superior to the medium-temperature heat pump working fluids widely used in the market. This can effectively reduce the compressor manufacturing cost and improve the safety of operation.

[0020] 3. The compressor of this pentane distillation heat pump coupling energy-saving method adopts frequency conversion to adapt to changes in production load, which can completely eliminate other external heat sources at the bottom of the distillation column; the compression ratio is adjusted by controlling the compressor outlet pressure, which can improve the electrothermal conversion efficiency of the heat pump process and realize the closed-loop circulation of cold and heat energy coupling in the distillation process.

[0021] 4. The low-pressure / low-temperature oil and gas at the top of the pentane distillation column, which serves as the working fluid for the heat pump, exchanges heat with the high-temperature oil and gas at the top of the column after condensation in the reboiler at the bottom of the column. After the heat recovery temperature is increased, the temperature difference required for compression by the compressor to the bottom of the column for reboiler is reduced. This can effectively reduce the compression ratio of the compressor and improve the mechanical conversion efficiency of the heat pump process.

[0022] 5. The heat pump COP of the pentane distillation heat pump coupling energy-saving method can be increased to over 6.0 after application, and the energy saving rate exceeds 60% and the carbon emission reduction rate exceeds 70% compared with the traditional distillation process.

[0023] 6. An apparatus for a pentane distillation heat pump coupling energy-saving method, comprising adding an oil-free lubricated adiabatic compressor suitable for pentane gas phase components to the traditional pentane distillation system process. The oil-free compressor adopts frequency conversion to adapt to changes in production load, and the compression ratio and outlet temperature of the oil-free lubricated adiabatic compressor are adjusted by outlet pressure control. The original distillation column top condenser is replaced with a column top oil-gas heat exchanger, and the heat source medium of the column bottom reboiler is replaced with high-temperature / high-pressure column top oil-gas compressed by the oil-free lubricated adiabatic compressor. A feed heat exchanger is added to the process to further recover the waste heat of the column top oil-gas outlet after condensation. The above equipment is connected by metal pipes to form a system to couple the energy (heat and cold) used in pentane distillation. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 This is a flowchart illustrating the principles of conventional distillation of pentane.

[0026] Figure 2 This is a flowchart illustrating the principle of energy-saving methods for pentane distillation coupled with heat pumps. Detailed Implementation

[0027] Comparative Example:

[0028] A factory's pentane unit uses a conventional distillation process to extract F3 pentane foaming agent products with a total pentane content ≥99.0%, isopentane 70±2%, and n-pentane 30±2% from saturated light naphtha or reformate topping oil components (see Table 1) that are lighter than pentane. The reboiler at the bottom of the column uses 0.7MPa, 185℃ steam as the heat source and circulating cooling water as the cold source to condense and cool the oil and gas at the top of the column.

[0029] (See attached) Figure 1 The conventional distillation production process for the F3 pentane foaming agent product in this unit is as follows: The low-pressure / low-temperature oil and gas (0.12MPa, 55℃) from the top of the pentane distillation column 1 is condensed and cooled to 45℃ by heat exchanger 2 with external circulating water and then enters the reflux tank 3. Part of the condensed and cooled 45℃ liquid oil from the top of the column in the reflux tank 3 is returned to the top of the pentane distillation column 1 as reflux (reflux ratio 3.23), and the other part is collected as the F3 pentane foaming agent product.

[0030] The reboiler 4 at the bottom of the pentane distillation column uses externally supplied steam at 0.7 MPa and 185°C as a heat source.

[0031] Table 1: Raw materials containing saturated light naphtha or reformed top oil components (mass percentage) after removal of pentane-lighter components:

[0032]

[0033] Example 1

[0034] A factory's pentane distillation unit uses F3 pentane foaming agent, which is extracted from saturated light naphtha or reformed topping oil fractions that are lighter than pentane. The total amount of pentane (mass ratio) is ≥99.0%, isopentane 70±2%, and n-pentane 30±2%. The raw material composition, feed rate, reflux ratio, and product quality separation requirements are consistent with those of the comparative example. In the heat pump process, an oil-free lubricated screw compressor is used to convert low-temperature heat into high-temperature heat.

[0035] (See attached) Figure 2 The energy-saving process of the F3 pentane foaming agent product distillation heat pump coupling in this device is as follows: The low-pressure / low-temperature oil and gas (0.12MPa, 55℃) from the top of the pentane distillation column 1 exchanges heat with the high-pressure / high-temperature liquid (0.39 MPa, 81℃) phase oil and gas from the bottom of the pentane distillation column 4 after being condensed by the oil-gas heat exchanger 2 at the top of the column. After the temperature is reduced to 65℃, it enters the oil-free screw compressor 5 with variable frequency load regulation. The compression ratio and outlet temperature of the compressor are adjusted by outlet pressure control. The high-pressure / high-temperature (0.40 MPa, 92℃) vapor phase oil and gas components from the outlet of the oilless screw compressor 5 enter the reboiler 4 at the bottom of the pentane distillation column as a heat source. After heat exchange and condensation with the bottom oil, the high-pressure / high-temperature liquid phase (0.39 MPa, 81℃) oil and gas components from the top of the column first exchange heat with the low-pressure / low-temperature (0.12 MPa, 55℃) oil and gas at the top of the pentane distillation column 1 via the top oil and gas heat exchanger 2. Then, they enter the feed heat exchanger 6 and exchange heat with the feed to the pentane distillation column 1 to cool to 51℃ before entering the distillation system reflux tank 3. After condensation and cooling, part of the liquid phase oil product from the top of the column in the reflux tank 3 is returned to the top of the pentane distillation column 1 as reflux (reflux ratio 3.23), and the other part is collected as F3 pentane foaming agent product.

[0036] Table 2: Comparison of energy-saving results of conventional distillation and heat pump coupling methods for pentane F3 foaming agent products:

[0037]

[0038] The energy consumption conversion value adopts the "Standard for Energy Consumption Calculation in Petrochemical Design" GB / T 50441-2016; the value of the electricity emission factor is taken from the "Announcement on the Release of Carbon Dioxide Emission Factors for Electricity in 2022" (Ministry of Ecology and Environment, December 20, 2024) Jiangsu Province's average carbon dioxide emission factor for purchased electricity.

[0039] The product quality of the pentane F3 foaming agent produced by the heat pump coupling method of the present invention is consistent with that of the conventional distillation method in the comparative embodiment.

[0040] Furthermore, the COP value of the pentane F3 blowing agent product produced by the heat pump coupling method of this invention is 8.05, which is at an industry-leading level. The energy consumption of the pentane F3 blowing agent product produced by the heat pump coupling method of this invention is reduced by 73% compared to the conventional distillation method, and the carbon emission rate of the pentane F3 blowing agent product produced by the heat pump coupling method of this invention is reduced by 81% compared to the conventional distillation method. This invention generates significant economic benefits and demonstrates remarkable progress.

[0041] Example 2

[0042] (See attached) Figure 2 A certain factory's pentane distillation unit uses F3 pentane foaming agent products extracted from saturated light naphtha or reformed topping oil fractions that are lighter than pentane, with a total pentane content of ≥99.0%, isopentane 70±2%, and n-pentane 30±2%. The raw material composition, feed rate, reflux ratio, and product quality separation requirements are consistent with those of the comparative example. In the heat pump process, an oil-free lubricated reciprocating compressor is used to convert low-temperature heat into high-temperature heat.

[0043] The energy-saving process of the F3 pentane foaming agent product distillation heat pump coupling in this device is as follows: The low-pressure / low-temperature (0.12MPa, 55℃) oil and gas from the top of the pentane distillation column 1 is condensed at the outlet of the high-pressure / high-temperature (0.40 MPa, 81℃) liquid phase oil and gas component at the top of the column through the top oil and gas heat exchanger 2 and the bottom reboiler 4 of the pentane distillation column, and then enters the oil-free reciprocating compressor 5 with variable frequency load regulation. The compression ratio and outlet temperature of the compressor are adjusted by the outlet pressure control method. The high-pressure / high-temperature (0.42MPa, 92℃) vapor phase oil and gas components from the outlet of the oilless reciprocating compressor 5 enter the reboiler 4 at the bottom of the pentane distillation column as a heat source. After being condensed by the bottom oil heat exchanger, the high-pressure / high-temperature liquid phase (0.40 MPa, 81℃) oil and gas components from the top of the column first exchange heat with the low-pressure / low-temperature (0.12MPa, 55℃) oil and gas at the top of the pentane distillation column 1 through the top oil-gas heat exchanger 2. Then, it enters the feed heat exchanger 6 and exchanges heat with the feed of the pentane distillation column 1 to cool it to 51℃ before entering the original distillation system reflux tank 3. After being condensed and cooled, part of the top liquid phase oil in the reflux tank 3 is returned to the top of the pentane distillation column 1 as reflux (reflux ratio 3.23), and the other part is collected as F3 pentane foaming agent product.

[0044] Table 3: Comparison of energy-saving results of conventional distillation and heat pump coupling methods for pentane F3 foaming agent products:

[0045]

[0046] The energy consumption conversion value adopts the "Standard for Energy Consumption Calculation in Petrochemical Design" GB / T 50441-2016; the value of the electricity emission factor is taken from the "Announcement on the Release of Carbon Dioxide Emission Factors for Electricity in 2022" (Ministry of Ecology and Environment, December 20, 2024) Jiangsu Province's average carbon dioxide emission factor for purchased electricity.

[0047] The product quality of the pentane F3 foaming agent produced by the heat pump coupling method of the present invention is consistent with that of the conventional distillation method in the comparative embodiment.

[0048] Example 3

[0049] Using the same distillation process control conditions as the comparative example, the pentane distillation unit of a certain factory extracts n-pentane products with a content (mass ratio) ≥99.0% from saturated light naphtha or reformed topping oil components that are lighter than n-pentane. The raw material composition, feed rate, reflux ratio, and product quality separation requirements are the same as those in the comparative example. In the heat pump process, an oil-free lubricated turbo compressor is used to convert low-temperature heat into high-temperature heat.

[0050] (See attached) Figure 2 The energy-saving process of the n-pentane product distillation heat pump coupling in this unit is as follows: The low-pressure / low-temperature oil and gas (0.12 MPa, 60℃) from the top of the pentane distillation column 1 is condensed at the outlet of the high-pressure / high-temperature (0.52 MPa, 97℃) liquid phase oil and gas component at the top of the column through the top oil and gas heat exchanger 2 and the bottom reboiler 4 of the pentane distillation column, and then enters the oil-free lubricated turbo compressor 5 with variable frequency load regulation. The compressor compression ratio 3.10 and outlet temperature are adjusted by outlet pressure control. The high-pressure / high-temperature (0.54MPa, 113℃) vapor phase oil and gas components from the outlet of the oilless lubricated turbo compressor 5 enter the reboiler 4 at the bottom of the pentane distillation column as a heat source. After being condensed by the bottom oil heat exchanger, the high-pressure / high-temperature liquid phase (0.52 MPa, 97℃) oil and gas components from the top of the column first exchange heat with the low-pressure / low-temperature (0.12MPa, 60℃) oil and gas at the top of the pentane distillation column 1 through the top oil and gas heat exchanger 2. Then, it enters the feed heat exchanger 6 and exchanges heat with the feed of the pentane distillation column 1 to cool it to 56℃ before entering the original distillation system reflux tank 3. After being condensed and cooled, part of the liquid phase oil product from the top of the column in the reflux tank 3 is returned to the top of the pentane distillation column 1 as reflux (reflux ratio 0.91), and the other part is collected as n-pentane product.

[0051] Table 4: Feedstocks containing saturated light naphtha or reformed top oil components (mass percentage) after removal of components lighter than n-pentane:

[0052]

[0053] Table 5: Comparison of energy-saving results between conventional distillation and heat pump coupling methods for n-pentane products:

[0054]

[0055] The energy consumption conversion value adopts the "Standard for Energy Consumption Calculation in Petrochemical Design" GB / T 50441-2016; the value of the electricity emission factor is taken from the "Announcement on the Release of Carbon Dioxide Emission Factors for Electricity in 2022" (Ministry of Ecology and Environment, December 20, 2024) Jiangsu Province's average carbon dioxide emission factor for purchased electricity.

[0056] The product quality of the n-pentane produced by the heat pump coupling method of the present invention is consistent with that of the conventional distillation method in the comparative embodiment.

[0057] The present invention is not limited to the specific technical solutions described in the above embodiments. All technical solutions formed by equivalent substitutions are within the scope of protection claimed by the present invention.

Claims

1. A pentane distillation heat pump coupling energy-saving method, characterized in that: The pentane distillation heat pump coupling energy-saving method involves three heat exchangers and one oil-free adiabatic compressor (5) integrated into the pentane distillation system process to couple the heat and cold energy used in pentane distillation. The oil-free adiabatic compressor (5) in the heat pump process adopts an oil-free screw compressor, reciprocating compressor, or turbine compressor. One top oil-gas heat exchanger (2) in the heat pump process is used to exchange heat between the low-pressure / low-temperature oil-gas from the top of the pentane distillation column (1) and the high-pressure / high-temperature liquid phase top oil-gas components condensed at the outlet of the bottom reboiler (4) of the pentane distillation column. One heat exchanger is the bottom reboiler (4) of the distillation column, used to heat the bottom oil of the column with the high-pressure / high-temperature gas phase top oil-gas components from the compressor outlet. One feed heat exchanger (6) is used to exchange heat between the feed of the pentane distillation column and the high-pressure liquid phase top oil-gas components condensed from the top oil-gas heat exchanger (2). Waste heat is recovered; the compressor adopts frequency conversion to adapt to changes in production load, and the compression ratio and outlet temperature of the compressor are adjusted by outlet pressure control; the saturated phase low-pressure 0.08~0.20MPa / low-temperature oil and gas at the top of the pentane distillation column (1) is directly used as the working fluid of the heat pump. It first passes through the top oil and gas heat exchanger (2) and the bottom reboiler (4) to condense the high-temperature liquid phase top oil and gas to recover heat; after heat exchange and heating, the oil and gas at the top of the low-pressure pentane distillation column (1) is adiabatically compressed by the oilless lubricated adiabatic compressor (5) with a compression ratio of 2.0-4.0 and then enters the bottom reboiler (4) of the pentane distillation column as a heat source. It first exchanges heat with the bottom oil and then condenses. After passing through the top oil and gas heat exchanger (2) and the low-pressure / low-temperature oil and gas at the top of the pentane distillation column (1), the raw material heat exchanger (6) and the raw material of the distillation column for heat exchange and cooling before entering the reflux tank (3).

2. The pentane rectification heat pump coupled energy saving process of claim 1, wherein: The pentane distillation heat pump coupling energy-saving device consists of a pentane distillation column (1), a top oil-gas heat exchanger (2), a reflux tank (3), a bottom reboiler (4), an oil-free lubricated insulated compressor (5), a raw material heat exchanger (6), a frequency converter controller for the oil-free lubricated insulated compressor (5), and a compressor outlet pressure control circuit. These components are connected by metal pipes to form a single system that couples the heat and cold energy used in pentane distillation. The saturated oil-gas at the top of the pentane distillation column (1) first passes through the top oil-gas heat exchanger (2) and then through the bottom reboiler (4) to exchange heat with the high-temperature liquid phase at the top of the column to recover heat. After being adiabatically compressed and heated by the oilless lubricating adiabatic compressor (5), it enters the reboiler (4) at the bottom of the pentane distillation column as a heat source. After heat exchange and condensation with the bottom oil, it passes through the top oil-gas heat exchanger (2) and the top oil-gas of the pentane distillation column (1), and the raw material heat exchanger (6) and the raw material of the distillation column for heat exchange and cooling before entering the reflux tank (3). After being collected from the reflux tank (3), part of it is returned to the pentane distillation column (1) from the top as reflux, and the other part is collected as product. The oilless lubricating adiabatic compressor (5) adopts frequency conversion to adapt to changes in production load, and the compressor compression ratio and outlet temperature are adjusted by outlet pressure control.

3. The pentane distillation heat pump coupling energy-saving method according to claim 2, characterized in that: The energy-saving process of pentane foaming agent product distillation heat pump coupling is as follows: The low-pressure / low-temperature oil and gas (0.12 MPa, 55℃) from the top of the pentane distillation column (1) is heated by the high-pressure / high-temperature liquid phase (0.39 MPa, 81℃) condensed at the outlet of the pentane distillation column bottom reboiler (4) to 65℃, and then enters the oil-free screw compressor with variable frequency load regulation. The compressor compression ratio and outlet temperature are adjusted by outlet pressure control. The high-pressure / high-temperature (0.40 MPa, 92℃) gas phase oil and gas phase from the outlet of the oil-free screw compressor enters the pentane distillation column bottom reboiler (4) as a heat source, and is heated by the high-pressure / high-temperature liquid phase (0.39 MPa, 81℃) condensed at the outlet of the pentane distillation column bottom reboiler (4). The MPa, 81℃ top oil and gas components first exchange heat with the pentane distillation column 1 at a low pressure / low temperature of 0.12MPa, 55℃ through the top oil and gas heat exchanger 2. Then, they enter the feed heat exchanger (6) and exchange heat with the feed of the pentane distillation column (1) to cool to 51℃ before entering the distillation system reflux tank (3). A portion of the top liquid oil in the reflux tank (3) after condensation and cooling is returned to the top of the pentane distillation column (1) as reflux with a reflux ratio of 3.

23. The other portion is collected as F3 pentane foaming agent product.

4. The pentane distillation heat pump coupling energy-saving method according to claim 2, characterized in that: The energy-saving process of pentane foaming agent product distillation heat pump coupling is as follows: The low-pressure / low-temperature oil and gas at 0.12 MPa and 55°C from the top of the pentane distillation column (1) is condensed at the outlet of the pentane distillation column bottom reboiler (4) via the top oil and gas heat exchanger (2) to 65°C, and then enters the oil-free reciprocating compressor with variable frequency load regulation. The compressor compression ratio and outlet temperature are adjusted by outlet pressure control. The high-pressure / high-temperature gas at 0.42 MPa and 92°C from the outlet of the oil-free reciprocating compressor enters the pentane distillation column bottom reboiler (4) as a heat source, and the high-pressure / high-temperature liquid phase 0.40 MPa and 81°C from the bottom oil are condensed. The MPa, 81℃ top oil and gas components first exchange heat with the 0.12MPa, 55℃ oil and gas at the low pressure / low temperature of the top of the pentane distillation column 1 via the top oil and gas heat exchanger 2. Then, they enter the feed heat exchanger (6) to exchange heat with the feed of the pentane distillation column 1 and cool to 51℃ before entering the original distillation system reflux tank (3). Part of the top liquid phase oil in the reflux tank (3) after condensation and cooling is returned to the top of the pentane distillation column (1) from the top of the column as reflux with a reflux ratio of 3.

23. The other part is collected as F3 pentane foaming agent product.

5. The pentane distillation heat pump coupling energy-saving method according to claim 2, characterized in that: The energy-saving process of pentane product distillation heat pump coupling is as follows: The low-pressure / low-temperature oil and gas at 0.12 MPa and 60°C from the top of the pentane distillation column (1) is condensed at the outlet of the pentane distillation column bottom reboiler (4) via the top oil and gas heat exchanger (2) to the high-pressure / high-temperature liquid phase at 0.52 MPa and 97°C, and then enters the oil-free turbo compressor with variable frequency load regulation. The compressor compression ratio and outlet temperature are adjusted by outlet pressure control. The high-pressure / high-temperature gas phase at 0.54 MPa and 113°C from the outlet of the oil-free turbo compressor enters the pentane distillation column bottom reboiler (4) as a heat source. The high-pressure / high-temperature liquid phase at 0.52 MPa and 97°C from the bottom oil is condensed at the outlet of the oil-free turbo compressor. The oil and gas components at the top of the column, at MPa and 97℃, first exchange heat with the oil and gas at the low pressure / low temperature level of 0.12MPa and 60℃ at the top of the pentane distillation column (1) through the top oil and gas heat exchanger (2). Then, they enter the feed heat exchanger (6) to exchange heat with the feed of the pentane distillation column (1) and are cooled to 56℃ before entering the original distillation system reflux tank (3). Part of the liquid phase oil product at the top of the column after condensation and cooling in the reflux tank (3) is returned to the top of the pentane distillation column (1) from the top of the column as reflux with a reflux ratio of 0.

91. The other part is collected as n-pentane product.

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