A device and process for producing high-purity alkanes by refining LPG using multi-tower coupling distillation

Abstract

The present invention provides a device and a process for producing high-purity alkanes by refining LPG with multi-tower coupling distillation, which belongs to the field of petrochemical technology. The device includes a mixed hydrocarbon storage tank for holding raw materials, and also includes a propane preparation device connected to the mixed hydrocarbon storage tank and used to prepare propane; an isobutane preparation device connected to the output end of the propane preparation device and used to prepare isobutane; a normal butane preparation device connected to the isobutane preparation device and used to prepare normal butane; and a refrigeration device connected to the propane preparation device, the isobutane preparation device and the normal butane preparation device and used to provide a cold source. The present invention separates the effective components in the LPG raw material step by step through multi-tower coupling distillation to obtain a variety of high-purity alkane products. The process is simple and smooth, the extraction rate is high, the product purity is high, and the operation is stable; a fully physical production process is adopted, no new impurities are introduced, no pollution, and the process safety factor is high.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical industry, and in particular to a device and a process for producing high-purity alkanes by using multi-tower coupled distillation to purify LPG. Background Art

[0002] Liquefied petroleum gas (LPG), the main components of LPG are propane and butane, with a small amount of olefins. LPG is stored in a tank container in liquid form under appropriate pressure and is often used as a cooking fuel, which is the liquefied gas we often use. LPG has been used as a light vehicle fuel for many years, and LPG can also be stored in tanks to provide fuel for cars. High-purity alkanes are widely used as standard gases, calibration gases, online instrument standard gases, and the preparation of certain special mixed gases in industrial sectors such as chemical, metallurgical, electronic, and petroleum, as well as in basic research, air pollution monitoring, aviation, and atomic energy, and have very high market value. The preparation of high-purity alkanes usually adopts distillation separation, which is based on the different boiling points of the substances and is a process of multiple condensation and evaporation to achieve the purpose of separating the mixed components. It is widely used in the processing of petrochemical products and is one of the indispensable process methods for petroleum refining companies. At present, the heat source of the reboiler of the petrochemical product distillation tower is generally heated to 80°C by steam, and the top of the tower is cooled to about 45°C by circulating water. Due to the high tower temperature, the tower pressure needs to be controlled at about 2.0MPa. Under higher pressure, the relative separation of each component is greatly reduced, and it is difficult to extract high-purity products. In addition, the tower bottom temperature is high, and steam heating is required, which consumes additional fuel to produce steam and increases production costs. In addition, higher operating pressure also increases safety risks.

[0003] In order to overcome the above defects, it is necessary to provide a device and a production process for refining LPG to produce high-purity alkanes that is safe, low in energy consumption, stable in production, and easy to operate. Summary of the invention

[0004] In view of this, the present invention provides a device and process for producing high-purity alkanes by refining LPG through multi-tower coupling distillation, which has simple structure, reasonable process design, easy operation, high product yield, and energy saving and consumption reduction.

[0005] In order to achieve the above technical effects, the present invention provides a device and process for producing high-purity alkanes by refining LPG by multi-tower coupling distillation, which adopts the following technical scheme:

[0006] A device for producing high-purity alkanes by refining LPG by multi-tower coupling distillation, comprising a mixed hydrocarbon storage tank for containing raw materials, characterized in that it also includes:

[0007] A propane production device, which is connected to the mixed hydrocarbon storage tank and is used to prepare propane;

[0008] an isobutane production device, the isobutane production device is connected to the output end of the propane production device and is used to prepare isobutane;

[0009] A normal butane production device, which is connected to the isobutane production device and is used to prepare normal butane;

[0010] A refrigeration device is connected to the propane production device, the isobutane production device and the normal butane production device and is used to provide a cold source.

[0011] Furthermore, the propane production equipment includes a deethanizer connected to the mixed hydrocarbon storage tank through a pipeline, a propane tower connected to the liquid discharge port at the bottom of the deethanizer through a pipeline, a first gas-liquid separation mechanism connected to the top of the deethanizer through a pipeline and used to cool the top steam of the deethanizer and perform gas-liquid separation, and a second gas-liquid separation mechanism connected to the top of the propane tower and used to cool the top steam of the propane tower and perform gas-liquid separation;

[0012] The top steam of the deethanizer is refluxed into the deethanizer through the reflux liquid separated by the first gas-liquid separation mechanism, and the top steam of the propane tower is refluxed into the propane tower through the reflux liquid separated by the second gas-liquid separation mechanism;

[0013] The liquid inlet of the propane tower is connected to the propane intermediate storage tank through a pipeline, and the liquid discharge port of the propane intermediate storage tank is connected to the propane storage tank through a 2# shielded pump.

[0014] Furthermore, the first gas-liquid separation mechanism includes a 1# top condenser connected to the top of the deethanizer through a pipeline, a 1# separator connected to the discharge port of the 1# top condenser through a pipeline, the discharge port of the 1# separator is connected to the reflux port of the deethanizer through a pipeline, the gas discharged from the top of the deethanizer is liquefied by the 1# top condenser and then enters the 1# separator for gas-liquid separation, the liquid phase enters the reflux port at the top of the deethanizer as a reflux liquid, and the gas phase is sent to the tail gas main pipe;

[0015] The second gas-liquid separation mechanism includes a 2# top condenser connected to the top of the propane tower through a pipeline, and a 2# separator connected to the discharge port of the 2# top condenser through a pipeline. The discharge port of the 2# top condenser is connected to the reflux port of the propane tower through a pipeline. After the gas discharged from the top of the propane tower is liquefied by the 2# top condenser, the liquid phase enters the reflux port at the top of the propane tower as reflux liquid.

[0016] Furthermore, the isobutane production equipment includes a depropanizer connected to the propane production equipment through a pipeline, an isobutane tower connected to the discharge port at the bottom of the depropanizer through an 8# shielded pump, an isobutane intermediate storage tank connected to the liquid intake port of the isobutane tower through a pipeline, and an isobutane storage tank connected to the isobutane intermediate storage tank through a 4# shielded pump;

[0017] The top of the depropanizer is connected to the 2# top condenser through a pipeline, and the discharge port of the 2# separator is connected to the reflux port of the depropanizer through a pipeline. The gas discharged from the top of the depropanizer is liquefied by the 2# top condenser and then enters the 2# separator for gas-liquid separation. The liquid phase enters the reflux port at the top of the depropanizer as reflux liquid, and the gas phase is sent to the tail gas main pipe. After the top gas of the isobutane tower is liquefied by the 3# top condenser, the liquid phase is refluxed to the reflux port of the isobutane tower as reflux liquid.

[0018] Furthermore, the liquid discharge port at the bottom of the isobutane tower is connected to the pentane-rich storage tank and the normal butane production equipment through pipelines.

[0019] Furthermore, the n-butane production equipment includes a deisobutane tower connected to the isobutane production equipment through a pipeline, a n-butane tower connected to the liquid discharge port at the bottom of the deisobutane tower through a 7# shielded pump, a n-butane intermediate storage tank connected to the liquid intake port of the n-butane tower through a pipeline, a n-butane storage tank connected to the n-butane intermediate storage tank through a 6# shielded pump, and a third gas-liquid separation mechanism connected to the top of the deisobutane tower and the top of the n-butane tower through a pipeline, the reflux liquid separated by the third gas-liquid separation mechanism is refluxed to the reflux port of the deisobutane tower and the reflux port of the n-butane tower respectively, and the bottom of the n-butane tower is connected to the LPG residual liquid storage tank through a 5# shielded pump.

[0020] Furthermore, the third gas-liquid separation mechanism includes a 4# top condenser and a 3# separator connected to the discharge port of the 4# top condenser through a pipeline, the discharge port of the 3# separator is connected to the top reflux port of the deisobutanizer through a pipeline, the discharge port of the 4# top condenser is connected to the reflux port of the normal butane tower through a pipeline, the gas discharged from the top of the deisobutanizer tower is liquefied through the 4# top condenser and then enters the 3# separator for gas-liquid separation, the liquid phase enters the reflux port at the top of the deisobutanizer tower as reflux liquid, and the gas phase is sent to the tail gas main pipe.

[0021] Furthermore, the refrigeration equipment includes a circulating ice machine, an evaporative condenser connected to the circulating ice machine through a pipeline, and a refrigerant storage tank connected to the outlet of the evaporative condenser;

[0022] The refrigerant storage tank uses the cooled condensing agent for refrigeration of the propane production equipment, isobutane production equipment and normal butane production equipment. The refrigerant after refrigeration by the propane production equipment, isobutane production equipment and normal butane production equipment enters the circulating ice machine and evaporative condenser for cooling treatment.

[0023] A process for producing high-purity alkanes by using multi-tower coupled distillation to purify LPG, using the above-mentioned device for producing high-purity alkanes by using multi-tower coupled distillation to purify LPG, comprises the following steps:

[0024] Step 1, adding raw materials to a propane production device to obtain propane and simultaneously obtain a first mixed raw material;

[0025] Step 2, adding the first mixed raw material of step 1 into an isobutane preparation device to obtain isobutane and rich pentane, and at the same time obtain a second mixed raw material;

[0026] Step 3: Add the second mixed raw material in step 2 to the n-butane production equipment to obtain n-butane and LPG residual liquid.

[0027] The above technical solution of the present invention includes at least the following beneficial effects:

[0028] 1. Through multi-tower coupled distillation, the effective components in the LPG raw materials are separated step by step to obtain a variety of high-purity alkane products. The process is simple and smooth, the extraction rate is high, the product purity is high, and the operation is stable;

[0029] 2. Adopting a fully physical production process, no new impurities are introduced, no pollution, and high process safety factor;

[0030] 3. The use of large specific surface area structured packing has the effects of small resistance drop, high separation efficiency and wide operating flexibility;

[0031] 4. According to the physical and chemical characteristics of C3-C5, the evaporation of the refrigerant is selected as the cold source of the tower top reflux, which can achieve a temperature of -20℃ or even lower, and reduce the tower pressure to 0.3MPa or slightly positive pressure, thereby increasing the separation degree of each component, which is beneficial to the improvement of product purity. The tower bottom temperature can also be reduced to room temperature, and the compressed refrigerant gas liquefaction heat release potential replaces steam as the reboiler heat source. The liquefied refrigerant evaporates at the top of the tower as the cold source of reflux, forming a refrigeration and heating cycle based on the heat pump distillation principle, which not only reduces production costs, but also greatly improves the safety and reliability of the device at a lower operating pressure;

[0032] 5. This process is continuous distillation, which can achieve long-term safe and stable operation of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a process flow chart in an embodiment of the present invention;

[0034] In the figure:

[0035] 1. Mixed hydrocarbon storage tank; 2. Deethanizer; 3. 1# top condenser; 4. 1# separator; 5. Propane tower; 6. 2# top condenser; 7. 2# separator; 8. Depropanizer; 9. 8# shielded pump; 10. 5# shielded pump; 11. Isobutane tower; 12. 3# top condenser; 13. 1# shielded pump; 14. Propane intermediate storage tank; 15. 2# shielded pump; 16. 3# shielded pump; 1 7. Isobutane intermediate storage tank; 18. 4# shielded pump; 19. Deisobutanizer; 20. 7# shielded pump; 21. Normal butane tower; 22. 4# top condenser; 23. 3# separator; 24. Refrigerant gas-liquid separator; 25. Normal butane intermediate storage tank; 26. 6# shielded pump; 27. 4# separator; 28. Evaporative condenser; 29. ​​Refrigerant storage tank; 30. Circulating ice machine; 31. Oil separator. DETAILED DESCRIPTION

[0036] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1 , the technical scheme of the embodiment of the present invention is clearly and completely described. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1 As shown: a device for producing high-purity alkanes by distilling and refining LPG using multiple towers, including a mixed hydrocarbon storage tank 1 for containing raw materials, and a propane preparation device connected to the mixed hydrocarbon storage tank 1 and used for preparing propane;

[0039] an isobutane production device connected to the output end of the propane production device and used for producing isobutane;

[0040] A normal butane production device, connected to the isobutane production device and used for producing normal butane;

[0041] The refrigeration equipment is connected to the propane production equipment, the isobutane production equipment and the normal butane production equipment and is used to provide a cold source.

[0042] The propane production equipment includes a deethanizer 2 connected to a mixed hydrocarbon storage tank 1 through a pipeline, a propane tower 5 connected to a liquid discharge port at the bottom of the deethanizer 2 through a pipeline, a first gas-liquid separation mechanism connected to the top of the deethanizer 2 through a pipeline and used for cooling the top steam of the deethanizer 2 and performing gas-liquid separation, and a second gas-liquid separation mechanism connected to the top of the propane tower 5 and used for cooling the top steam of the propane tower 5 and performing gas-liquid separation. The top steam of the deethanizer 2 is refluxed into the deethanizer 2 through the reflux liquid separated by the first gas-liquid separation mechanism, and the top steam of the propane tower 5 is refluxed into the propane tower 5 through the reflux liquid separated by the second gas-liquid separation mechanism; the liquid intake port of the propane tower 5 is connected to a propane intermediate storage tank 14 through a pipeline, and the liquid discharge port of the propane intermediate storage tank 14 is connected to the propane storage tank through a 2# shielded pump 15. The first gas-liquid separation mechanism includes a 1# top condenser 3 connected to the top of the deethanizer 2 through a pipeline, a 1# separator 4 connected to the discharge port of the 1# top condenser 3 through a pipeline, the discharge port of the 1# separator 4 is connected to the reflux port of the deethanizer 2 through a pipeline, the gas discharged from the top of the deethanizer 2 passes through the 1# top condenser 3 and is liquefied before entering the 1# separator 4 for gas-liquid separation, the liquid phase enters the reflux port at the top of the deethanizer 2 as a reflux liquid, and the gas phase is sent to the tail gas main pipe, the second gas-liquid separation mechanism includes a 2# top condenser 6 connected to the top of the propane tower 5 through a pipeline, a 2# separator 7 connected to the discharge port of the 2# top condenser 6 through a pipeline, the discharge port of the 2# top condenser 6 is connected to the reflux port of the propane tower 5 through a pipeline, the gas discharged from the top of the propane tower 5 passes through the 2# top condenser 6 and is liquefied before entering the 1# separator 4 as a reflux liquid.

[0043] The specific process of producing propane by propane production equipment is as follows: LPG raw material comes from mixed hydrocarbon storage tank 1, which is connected to the middle and upper inlet of deethanizer 2 through a pipeline. After entering deethanizer 2, the raw material undergoes mass transfer and heat transfer with the reflux liquid at the top of deethanizer 2. The temperature range of the reflux liquid is -5℃~-1℃. After mass transfer and heat transfer, the temperature range of the heavy component is 5℃~13℃. The heavy component accumulates continuously at the bottom of deethanizer 2, and the light component is heated and evaporated by the reboiler at the bottom of deethanizer 2. The temperature range of the reboiler heating is 5℃~13℃. It is discharged from the top of deethanizer 2 and enters 1# top condenser 3 through a pipeline to exchange heat with the refrigerant of 1# top condenser 3. After most of itself is liquefied, it enters 1# separator 4 through a pipeline for gas-liquid separation. The liquid phase enters the reflux port at the top of deethanizer 2 as reflux liquid, and the gas phase is sent to the tail gas main pipe. The liquid components at the bottom of deethanizer 2 are C3H867%, C2H6 0.5ppm, C4H 10-1 15%, C4H 10-213%, the rest are trace C5 and above components, the temperature is 5~13℃, the pressure is 4~5bar, most of the ethane in the raw material is removed; the liquid phase discharged from the bottom of the deethanizer 2 is connected to the middle inlet of the propane tower 5 through a pipeline, and the liquid phase discharged from the bottom of the deethanizer 2 undergoes mass transfer and heat transfer with the top reflux liquid of the propane tower 5, the temperature range of the reflux liquid is -13℃~-3℃, after mass transfer and heat transfer, the temperature range of the heavy component is 30℃~40℃, the heavy component continues to accumulate at the bottom of the propane tower 5, the light component is heated and evaporated by the reboiler at the bottom of the propane tower 5, the temperature range of the reboiler heating is 30℃~40℃, it is discharged from the top of the propane tower 5, and enters the 2# top condenser 6 through a pipeline, and exchanges heat with the refrigerant of the 2# top condenser 6, most of itself After being liquefied, it enters the reflux port of the propane tower through a pipeline. The temperature of the reflux liquid after liquefaction is -13℃~-3℃, and the pressure is 3~4.5bar. An overflow weir is arranged on the upper part of the propane tower 5, and the reflux liquid first enters the overflow weir. When the liquid level is higher than the overflow weir baffle, it overflows from the top of the propane tower 5 to the bottom of the propane tower 5. A liquid intake port is arranged at the lower part of the overflow weir, and the propane product is obtained by controlling the regulating valve. The propane liquid intake port is connected to the propane intermediate storage tank 14 through a pipeline, and the liquid phase is sent to the propane storage tank through the 2# shielded pump 15. The purity of the propane product is above 99.995%, the temperature is -5~-10℃, and the pressure is 3.2~4bar. The extraction rate of propane can reach above 97%, and the gas phase returns to the top of the propane tower 5 to continue to be condensed and separated, thereby improving the product extraction rate.

[0044] The isobutane production equipment comprises a depropanizer 8 connected to the bottom of a propane tower 5 through a 1# shielded pump 13 and a pipeline, an isobutane tower 11 connected to the discharge port at the bottom of the depropanizer 8 through an 8# shielded pump 9, an isobutane intermediate storage tank 17 connected to the liquid intake port of the isobutane tower 11 through a pipeline, and an isobutane storage tank connected to the isobutane intermediate storage tank 17 through a 4# shielded pump 18. The top of the depropanizer 8 is connected to a 2# top condenser 6 through a pipeline, and the discharge port of the 2# separator 7 is connected to the reflux port of the depropanizer 8 through a pipeline. The gas discharged from the top of the depropanizer 8 is liquefied through the 2# top condenser 6 and then enters the 2# separator 7 for gas-liquid separation. The liquid phase enters the reflux port at the top of the depropanizer 5 as a reflux liquid, and the gas phase is sent to the tail gas main pipe. After the top gas of the isobutane tower 11 is liquefied through the 3# top condenser 12, the liquid phase refluxes to the reflux port of the isobutane tower 11 as a reflux liquid. The liquid discharge port at the bottom of the isobutane tower 11 is connected to the pentane-rich storage tank and the normal butane production equipment through pipelines.

[0045] The specific process of preparing isobutane by the isobutane preparation equipment is as follows: the liquid discharged from the bottom of the propane tower 5 is sent to the depropanizer 8 through the 1# shielded pump 13, enters from the middle of the depropanizer 8, and undergoes mass transfer and heat transfer with the reflux liquid at the top of the depropanizer 8. The temperature range of the reflux liquid is -11°C~-1°C. After mass transfer and heat transfer, the temperature range of the heavy component is 22°C~32°C. The heavy component accumulates continuously at the bottom of the depropanizer 8, and the light component is heated and evaporated by the reboiler at the bottom of the depropanizer 8. The temperature range of the reboiler heating is 22°C~32°C. It is discharged from the top of the depropanizer 8, enters the 2# top condenser 6 through a pipeline, exchanges heat with the refrigerant of the 2# top condenser 6, and most of itself is liquefied and enters the 2# separator 7 through a pipeline for gas-liquid separation. The liquid phase enters the reflux port at the top of the depropanizer 8 as reflux liquid, and the gas phase is sent to the tail gas main pipe. The liquid component at the bottom of the depropanizer 8 is C3H8 1ppm, C4H 10-1 48%, C4H 10-2 39%, the rest are trace C5 and above components, the temperature is 22℃~32℃, the pressure is 2.2~3.2bar, most of the propane in the raw material is removed; the liquid discharged from the bottom of the depropanizer 8 is sent to the isobutane tower 11 through the 8# shielded pump 8, enters from the middle and lower part of the isobutane tower 11, and undergoes mass transfer and heat transfer with the top reflux liquid of the isobutane tower 11. The temperature range of the reflux liquid is -13℃~-3℃. After mass transfer and heat transfer, the temperature range of the heavy component is 2℃~12℃, and the heavy component continues to accumulate at the bottom of the isobutane tower 11. The light component is heated and evaporated by the reboiler at the bottom of the isobutane tower 11. The temperature range of the reboiler heating is 2℃~12℃, and it is discharged from the top of the isobutane tower 11, enters the 3# top condenser 12 through a pipeline, and exchanges heat with the refrigerant of the 3# top condenser 12. Most of itself is liquid After liquefaction, the reflux liquid enters the reflux port of the isobutane tower 11 through a pipeline. The temperature of the liquefied reflux liquid is -13°C~-3°C, and the pressure is 1~1.3bar. An overflow weir is arranged at the top of the isobutane tower 11, and the reflux liquid first enters the overflow weir. When the liquid level is higher than the overflow weir baffle, it overflows from the top of the isobutane tower 11 to the bottom of the isobutane tower 11. A liquid intake port is arranged at the bottom of the overflow weir, and the isobutane product is obtained by controlling the regulating valve. The isobutane liquid intake port is connected to the isobutane intermediate storage tank 17 through a pipeline, and the liquid phase is sent to the isobutane storage tank through the 4# shielded pump 16. The purity of the isobutane product is above 99.995%, the temperature is -4~-11°C, and the pressure is 1.02~1.5bar. The extraction rate of isobutane can reach above 90%, and the gas phase returns to the top of the isobutane tower 11 to continue to be condensed and separated, thereby improving the product extraction rate.

[0046] The n-butane production equipment includes a deisobutanizer 19 connected to the isobutane tower 11 through a 3# shielded pump 15 and a pipeline, a n-butane tower 21 connected to the discharge port at the bottom of the deisobutanizer 19 through a 7# shielded pump 20, a n-butane intermediate storage tank 25 connected to the liquid intake port of the n-butane tower 21 through a pipeline, a n-butane storage tank connected to the n-butane intermediate storage tank 25 through a 6# shielded pump 26, and a third gas-liquid separation mechanism connected to the top of the deisobutanizer 19 and the top of the n-butane tower 21 through a pipeline. The reflux liquid separated by the third gas-liquid separation mechanism is refluxed to the reflux port of the deisobutanizer 19 and the reflux port of the n-butane tower 21 respectively, and the bottom of the n-butane tower 21 is connected to the LPG residual liquid storage tank through a 5# shielded pump 10. The third gas-liquid separation mechanism includes a 4# top condenser 22 and a 3# separator 23 connected to the discharge port of the 4# top condenser 22 through a pipeline. The discharge port of the 3# separator 23 is connected to the top reflux port of the deisobutanizer 19 through a pipeline. The discharge port of the 4# top condenser 22 is connected to the reflux port of the normal butane tower 21 through a pipeline. The gas discharged from the top of the deisobutanizer 19 is liquefied by the 4# top condenser 22 and then enters the 3# separator for gas-liquid separation. The liquid phase enters the reflux port at the top of the deisobutanizer 19 as a reflux liquid, and the gas phase is sent to the tail gas main pipe.

[0047] The specific process of producing n-butane in the n-butane production equipment is as follows: the liquid discharged from the bottom of the isobutane tower 11 is pressurized by the 3# shielded pump 16 and then divided into two paths, one of which is connected to the pentane-rich storage tank, and the other is sent to the deisobutanizer 19, entering from the middle and upper part of the deisobutanizer 19, and undergoing mass transfer and heat transfer with the top reflux liquid of the deisobutanizer 19. The temperature range of the reflux liquid is 10℃~18℃. After mass transfer and heat transfer, the temperature range of the heavy component is 22℃~32℃, and the heavy component is continuously accumulated at the bottom of the deisobutanizer 19. The light component is heated and evaporated by the reboiler at the bottom of the deisobutanizer 19. The temperature range of the reboiler heating is 22℃~32℃. It is discharged from the top of the deisobutanizer 19 and enters the 4# top condenser 22 through a pipeline. It exchanges heat with the refrigerant of the 4# top condenser 22. Most of itself is liquefied and enters the 3# separator 23 through a pipeline for gas-liquid separation. The liquid phase enters the top reflux port of the deisobutanizer 19 as reflux liquid, and the gas phase is sent to the tail gas main pipe. The liquid component at the bottom of the deisobutanizer 19 is C4H 10-1 75%, C5H 12-2 14%, C4H 10-20.2%, the rest are trace C5 and above components, the temperature is 22-32℃, the pressure is 1.7~2.6bar, most of the isobutane in the raw material is removed; the liquid discharged from the bottom of the deisobutane tower 19 is sent to the normal butane tower 21 through the 7# shielded pump, enters from the middle and lower part of the normal butane tower 21, and undergoes mass transfer and heat transfer with the top reflux liquid of the normal butane tower 21. The temperature range of the reflux liquid is 11℃~21℃. After mass transfer and heat transfer, the temperature range of the heavy component is 30℃~40℃, and the heavy component continues to accumulate at the bottom of the normal butane tower 21. The light component is heated and evaporated by the bottom reboiler of the normal butane tower 21. The temperature range of the reboiler heating is 30℃~40℃, and it is discharged from the top of the normal butane tower 21, enters the 4# top condenser 22 through a pipeline, and exchanges heat with the refrigerant of the 4# top condenser 22. After most of the body is liquefied, it enters the reflux port of the n-butane tower 21 through a pipeline. The temperature of the liquefied reflux liquid is 11°C~21°C, and the pressure is 1.2~2.3bar. An overflow weir is arranged at the top of the n-butane tower 21, and the reflux liquid first enters the overflow weir. When the liquid level is higher than the overflow weir baffle, it overflows from the top of the n-butane tower 21 to the bottom of the n-butane tower 21. A liquid intake port is arranged at the bottom of the overflow weir, and the n-butane product is obtained by controlling the regulating valve. The n-butane liquid intake port is connected to the n-butane intermediate storage tank through a pipeline, and the liquid phase is sent to the n-butane storage tank through a 6# shielded pump. The purity of the n-butane product is above 99%, the temperature is 10~20°C, and the pressure is 1.2~2.5bar. The extraction rate of n-butane can reach above 85%, and the gas phase returns to the top of the n-butane tower 21 to continue to be condensed and separated, thereby improving the product extraction rate.

[0048] The refrigeration equipment includes a circulating ice machine 30, an evaporative condenser 28 connected to the circulating ice machine 30 through a pipeline, and a refrigerant storage tank 29 connected to the outlet of the evaporative condenser 28. The refrigerant storage tank 29 uses the cooled condensing agent for refrigeration of the propane production equipment, the isobutane production equipment, and the normal butane production equipment. The refrigerant after refrigeration by the propane production equipment, the isobutane production equipment, and the normal butane production equipment enters the circulating ice machine and the evaporative condenser 28 for cooling treatment. The refrigeration equipment also includes a refrigerant gas-liquid separator 24 for separating the refrigerant into gas and liquid. The outlet of the refrigerant gas-liquid separator 24 The liquid port is connected to the refrigerant inlet of the circulating ice machine, the refrigerant inlet of the 4# top condenser 22, the refrigerant inlet of the 3# top condenser 12, the refrigerant inlet of the 1# top condenser 3, and the refrigerant inlet of the 4# separator 27 through a pipeline, the inlet of the refrigerant gas-liquid separator 24 is connected to the refrigerant outlet of the refrigerant storage tank 29 through a pipeline, the refrigerant outlet of the 4# top condenser 22 is connected to the inlet of the refrigerant gas-liquid separator 24 through a pipeline, and the refrigerant outlet of the 4# separator 27 is connected to the circulating ice machine 30 through a pipeline for cooling the refrigerant.

[0049] Example 2

[0050] A process for producing high-purity alkanes by refining LPG by multi-tower coupled distillation comprises the following steps:

[0051] Step 1, adding the raw material to the propane production equipment to obtain propane, and at the same time obtain the first mixed raw material; the specific steps are as follows: the LPG raw material comes from the mixed hydrocarbon storage tank 1, and is connected to the upper and middle inlet of the deethanizer 2 through a pipeline. After the raw material enters the deethanizer 2, mass transfer and heat transfer occur with the reflux liquid at the top of the deethanizer 2. The temperature range of the reflux liquid is -5°C to -1°C. After the mass transfer and heat transfer, the temperature range of the heavy component is 5°C to 13°C. The heavy component is continuously accumulated at the bottom of the deethanizer 2, and the light component is continuously accumulated at the bottom of the deethanizer 2. The components are heated and evaporated by the reboiler at the bottom of the deethanizer 2. The temperature range of the reboiler heating is 5℃~13℃. They are discharged from the top of the deethanizer 2 and enter the 1# top condenser 3 through a pipeline to exchange heat with the refrigerant of the 1# top condenser 3. Most of them are liquefied and enter the 1# separator 4 through a pipeline for gas-liquid separation. The liquid phase enters the top reflux port of the deethanizer 2 as reflux liquid, and the gas phase is sent to the tail gas main pipe. The liquid components at the bottom of the deethanizer 2 are C3H8 67%, C2H6 0.5ppm, C4H 10-1 15%, C4H 10-2 13%, the rest are trace C5 and above components, the temperature is 5~13℃, the pressure is 4~5bar, most of the ethane in the raw material is removed; the liquid phase discharged from the bottom of the deethanizer 2 is connected to the middle inlet of the propane tower 5 through a pipeline, and the liquid phase discharged from the bottom of the deethanizer 2 undergoes mass transfer and heat transfer with the top reflux liquid of the propane tower 5, the temperature range of the reflux liquid is -13℃~-3℃, after mass transfer and heat transfer, the temperature range of the heavy component is 30℃~40℃, the heavy component continues to accumulate at the bottom of the propane tower 5, the light component is heated and evaporated by the reboiler at the bottom of the propane tower 5, the temperature range of the reboiler heating is 30℃~40℃, it is discharged from the top of the propane tower 5, and enters the 2# top condenser 6 through a pipeline, and exchanges heat with the refrigerant of the 2# top condenser 6, most of itself After being liquefied, it enters the reflux port of the propane tower 5 through a pipeline. The temperature of the reflux liquid after liquefaction is -13℃~-3℃, and the pressure is 3~4.5bar. An overflow weir is arranged on the top of the propane tower 5, and the reflux liquid first enters the overflow weir. When the liquid level is higher than the overflow weir baffle, it overflows from the top of the propane tower 5 to the bottom of the propane tower 5. A liquid intake port is arranged at the bottom of the overflow weir, and the propane product is obtained by controlling the regulating valve. The propane liquid intake port is connected to the propane intermediate storage tank 14 through a pipeline, and the liquid phase is sent to the propane storage tank through the 2# shielded pump 15. The purity of the propane product is above 99.995%, the temperature is -5~-10℃, and the pressure is 3.2~4bar. The extraction rate of propane can reach above 97%, and the gas phase returns to the top of the propane tower 5 to continue to be condensed and separated, thereby improving the product extraction rate.

[0052] Step 2, adding the first mixed raw material of step 1 into the isobutane preparation equipment to obtain isobutane and rich pentane, and at the same time obtain the second mixed raw material; the specific steps are as follows: the liquid discharged from the bottom of the propane tower 5 is sent to the depropanizer 8 through the 1# shielded pump 13, enters the depropanizer 8 from the middle part, and undergoes mass transfer and heat transfer with the top reflux liquid of the depropanizer 8. The temperature range of the reflux liquid is -11°C to -1°C. After mass transfer and heat transfer, the temperature range of the heavy component is 22°C to 32°C. The heavy component is in the tower of the depropanizer 8. The light components are continuously accumulated at the bottom, and the light components are heated and evaporated by the reboiler at the bottom of the depropanizer 8. The temperature range of the reboiler heating is 22℃~32℃. The light components are discharged from the top of the depropanizer 8, and enter the 2# top condenser 6 through a pipeline to exchange heat with the refrigerant of the 2# top condenser 6. Most of the light components are liquefied and enter the 2# separator 7 through a pipeline for gas-liquid separation. The liquid phase enters the reflux port at the top of the depropanizer 8 as reflux liquid, and the gas phase is sent to the tail gas main pipe. The liquid components at the bottom of the depropanizer 8 are C3H8 1ppm, C4H 10-1 48%, C4H 10-2 39%, the rest are trace C5 and above components, the temperature is 22℃~32℃, the pressure is 2.2~3.2bar, most of the propane in the raw material is removed; the liquid discharged from the bottom of the depropanizer 8 is sent to the isobutane tower 11 through the 8# shielded pump 8, enters from the middle and lower part of the isobutane tower 11, and undergoes mass transfer and heat transfer with the top reflux liquid of the isobutane tower 11. The temperature range of the reflux liquid is -13℃~-3℃. After mass transfer and heat transfer, the temperature range of the heavy component is 2℃~12℃, and the heavy component continues to accumulate at the bottom of the isobutane tower 11. The light component is heated and evaporated by the reboiler at the bottom of the isobutane tower 11. The temperature range of the reboiler heating is 2℃~12℃, and it is discharged from the top of the isobutane tower 11, enters the 3# top condenser 12 through a pipeline, and exchanges heat with the refrigerant of the 3# top condenser 12. Most of itself is liquid After liquefaction, the reflux liquid enters the reflux port of the isobutane tower 11 through a pipeline. The temperature of the liquefied reflux liquid is -13°C~-3°C, and the pressure is 1~1.3bar. An overflow weir is arranged at the top of the isobutane tower 11, and the reflux liquid first enters the overflow weir. When the liquid level is higher than the overflow weir baffle, it overflows from the top of the isobutane tower 11 to the bottom of the isobutane tower 11. A liquid intake port is arranged at the bottom of the overflow weir, and the isobutane product is obtained by controlling the regulating valve. The isobutane liquid intake port is connected to the isobutane intermediate storage tank 17 through a pipeline, and the liquid phase is sent to the isobutane storage tank through the 4# shielded pump 16. The purity of the isobutane product is above 99.995%, the temperature is -4~-11°C, and the pressure is 1.02~1.5bar. The extraction rate of isobutane can reach above 90%, and the gas phase returns to the top of the isobutane tower 11 to continue to be condensed and separated, thereby improving the product extraction rate.

[0053] Step 3, adding the second mixed raw material in step 2 into the n-butane preparation equipment to obtain n-butane and LPG residual liquid at the same time, the specific steps are as follows: the liquid discharged from the bottom of the isobutane tower 11 is pressurized by the 3# shielded pump 16 and then divided into two paths, one path is connected to the pentane-rich storage tank, and the other path is sent to the deisobutanizer 19, enters from the middle and upper part of the deisobutanizer 19, and undergoes mass transfer and heat transfer with the top reflux liquid of the deisobutanizer 19. The temperature range of the reflux liquid is 10°C~18°C. After mass transfer and heat transfer, the temperature range of the heavy component is 22°C~32°C. The heavy component is The light components are continuously accumulated at the bottom of the deisobutanizer 19, and are heated and evaporated by the reboiler at the bottom of the deisobutanizer 19. The temperature range of the reboiler heating is 22°C~32°C, and the light components are discharged from the top of the deisobutanizer 19, and enter the 4# top condenser 22 through a pipeline, and exchange heat with the refrigerant of the 4# top condenser 22. Most of the light components are liquefied and enter the 3# separator 23 through a pipeline for gas-liquid separation. The liquid phase enters the top reflux port of the deisobutanizer 19 as reflux liquid, and the gas phase is sent to the tail gas main pipe. The liquid component at the bottom of the deisobutanizer 19 is C4H 10-1 75%, C5H 12-2 14%, C4H 10-2 0.2%, the rest are trace C5 and above components, the temperature is 22-32℃, the pressure is 1.7~2.6bar, most of the isobutane in the raw material is removed; the liquid discharged from the bottom of the deisobutane tower 19 is sent to the normal butane tower 21 through the 7# shielded pump, enters from the middle and lower part of the normal butane tower 21, and undergoes mass transfer and heat transfer with the top reflux liquid of the normal butane tower 21. The temperature range of the reflux liquid is 11℃~21℃. After mass transfer and heat transfer, the temperature range of the heavy component is 30℃~40℃, and the heavy component continues to accumulate at the bottom of the normal butane tower 21. The light component is heated and evaporated by the bottom reboiler of the normal butane tower 21. The temperature range of the reboiler heating is 30℃~40℃, and it is discharged from the top of the normal butane tower 21, enters the 4# top condenser 22 through a pipeline, and exchanges heat with the refrigerant of the 4# top condenser 22. After most of the body is liquefied, it enters the reflux port of the n-butane tower 21 through a pipeline. The temperature of the liquefied reflux liquid is 11°C~21°C, and the pressure is 1.2~2.3bar. An overflow weir is arranged at the top of the n-butane tower 21, and the reflux liquid first enters the overflow weir. When the liquid level is higher than the overflow weir baffle, it overflows from the top of the n-butane tower 21 to the bottom of the n-butane tower 21. A liquid intake port is arranged at the bottom of the overflow weir, and the n-butane product is obtained by controlling the regulating valve. The n-butane liquid intake port is connected to the n-butane intermediate storage tank through a pipeline, and the liquid phase is sent to the n-butane storage tank through a 6# shielded pump. The purity of the n-butane product is above 99%, the temperature is 10~20°C, and the pressure is 1.2~2.5bar. The extraction rate of n-butane can reach above 85%, and the gas phase returns to the top of the n-butane tower 21 to continue to be condensed and separated, thereby improving the product extraction rate.

[0054] In the present invention, unless otherwise clearly stipulated and limited, for example, it can be a fixed connection, a detachable connection, or an integrated one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, for ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0055] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A device for producing high-purity alkanes by refining LPG with multi-tower coupling distillation, comprising a mixed hydrocarbon storage tank for holding raw materials, characterized in that: Also includes: A propane production device, which is connected to the mixed hydrocarbon storage tank and is used to prepare propane; an isobutane production device, the isobutane production device is connected to the output end of the propane production device and is used to prepare isobutane; A normal butane production device, which is connected to the isobutane production device and is used to prepare normal butane; A refrigeration device, the refrigeration device is connected to the propane production device, the isobutane production device and the normal butane production device and is used to provide a cold source; The propane production equipment comprises a deethanizer connected to the mixed hydrocarbon storage tank via a pipeline, a propane tower connected to the liquid discharge port at the bottom of the deethanizer via a pipeline, a first gas-liquid separation mechanism connected to the top of the deethanizer via a pipeline and used to cool the top steam of the deethanizer and perform gas-liquid separation, and a second gas-liquid separation mechanism connected to the top of the propane tower and used to cool the top steam of the propane tower and perform gas-liquid separation; The top steam of the deethanizer is refluxed into the deethanizer through the reflux liquid separated by the first gas-liquid separation mechanism, and the top steam of the propane tower is refluxed into the propane tower through the reflux liquid separated by the second gas-liquid separation mechanism; The liquid inlet of the propane tower is connected to the propane intermediate storage tank through a pipeline, and the liquid discharge port of the propane intermediate storage tank is connected to the propane storage tank through a 2# shielded pump; The isobutane production equipment comprises a depropanizer connected to the propane production equipment through a pipeline, an isobutane tower connected to the liquid outlet at the bottom of the depropanizer through an 8# shielded pump, an isobutane intermediate storage tank connected to the liquid outlet of the isobutane tower through a pipeline, and an isobutane storage tank connected to the isobutane intermediate storage tank through a 4# shielded pump; The top of the depropanizer is connected to the 2# top condenser through a pipeline, and the discharge port of the 2# separator is connected to the reflux port of the depropanizer through a pipeline. The gas discharged from the top of the depropanizer is liquefied by the 2# top condenser and then enters the 2# separator for gas-liquid separation. The liquid phase enters the reflux port at the top of the depropanizer as reflux liquid, and the gas phase is sent to the tail gas main pipe. After the top gas of the isobutane tower is liquefied by the 3# top condenser, the liquid phase is refluxed to the reflux port of the isobutane tower as reflux liquid. The n-butane production equipment comprises a deisobutanizer connected to the isobutane production equipment through a pipeline, a n-butane tower connected to a liquid discharge port at the bottom of the deisobutanizer through a 7# shielded pump, a n-butane intermediate storage tank connected to a liquid intake port of the n-butane tower through a pipeline, a n-butane storage tank connected to the n-butane intermediate storage tank through a 6# shielded pump, and a third gas-liquid separation mechanism connected to the top of the deisobutanizer and the top of the n-butane tower through a pipeline, the reflux liquid separated by the third gas-liquid separation mechanism is refluxed to the reflux port of the deisobutanizer and the reflux port of the n-butane tower respectively, and the bottom of the n-butane tower is connected to an LPG residual liquid storage tank through a 5# shielded pump.

2. The device for producing high-purity alkanes by refining LPG using multi-tower coupled distillation according to claim 1, characterized in that: The first gas-liquid separation mechanism comprises a 1# top condenser connected to the top of the deethanizer through a pipeline, and a 1# separator connected to the discharge port of the 1# top condenser through a pipeline, the discharge port of the 1# separator is connected to the reflux port of the deethanizer through a pipeline, the gas discharged from the top of the deethanizer is liquefied by the 1# top condenser and then enters the 1# separator for gas-liquid separation, the liquid phase enters the reflux port at the top of the deethanizer as reflux liquid, and the gas phase is sent to the tail gas main pipe; The second gas-liquid separation mechanism includes a 2# top condenser connected to the top of the propane tower through a pipeline, and a 2# separator connected to the discharge port of the 2# top condenser through a pipeline. The discharge port of the 2# top condenser is connected to the reflux port of the propane tower through a pipeline. After the gas discharged from the top of the propane tower is liquefied by the 2# top condenser, the liquid phase enters the reflux port at the top of the propane tower as reflux liquid.

3. The device for producing high-purity alkanes by refining LPG using multi-tower coupled distillation according to claim 1, characterized in that: The liquid discharge port at the bottom of the isobutane tower is respectively connected to the pentane-rich storage tank and the normal butane production equipment through pipelines.

4. The device for producing high-purity alkanes by refining LPG using multi-tower coupled distillation according to claim 1, characterized in that: The third gas-liquid separation mechanism includes a 4# top condenser and a 3# separator connected to the discharge port of the 4# top condenser through a pipeline, the discharge port of the 3# separator is connected to the top reflux port of the deisobutanizer through a pipeline, the discharge port of the 4# top condenser is connected to the reflux port of the normal butane tower through a pipeline, the gas discharged from the top of the deisobutanizer tower is liquefied through the 4# top condenser and then enters the 3# separator for gas-liquid separation, the liquid phase enters the reflux port at the top of the deisobutanizer tower as reflux liquid, and the gas phase is sent to the tail gas main pipe.

5. The device for producing high-purity alkanes by refining LPG using multi-tower coupled distillation according to claim 1, characterized in that: The refrigeration equipment includes a circulating ice machine, an evaporative condenser connected to the circulating ice machine through a pipeline, and a refrigerant storage tank connected to the outlet of the evaporative condenser; The refrigerant storage tank uses the cooled condensing agent for refrigeration of the propane production equipment, isobutane production equipment and normal butane production equipment. The refrigerant after refrigeration by the propane production equipment, isobutane production equipment and normal butane production equipment enters the circulating ice machine and evaporative condenser for cooling treatment.

6. A process for producing high-purity alkanes by refining LPG using multi-tower coupled distillation, characterized in that: The device for producing high-purity alkanes by refining LPG using multi-tower coupled distillation as described in any one of claims 1 to 5 comprises the following steps: Step 1, adding raw materials to a propane production device to obtain propane and simultaneously obtain a first mixed raw material; Step 2, adding the first mixed raw material of step 1 into an isobutane preparation device to obtain isobutane and rich pentane, and at the same time obtain a second mixed raw material; Step 3: Add the second mixed raw material in step 2 to the n-butane production equipment to obtain n-butane and LPG residual liquid.

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