C4 separation device and process based on differential pressure thermal coupling and heat pump distillation technology

Abstract

A carbon four separation device and process based on differential pressure thermal coupling and heat pump distillation technology, the carbon four separation device includes a distillation system and a heat pump system; the distillation system includes a de-heavy tower, a de-light tower and a heat coupling reboiler, the heat coupling reboiler is arranged in the tower kettle of one of the de-heavy tower and the de-light tower, and the heat source inlet of the heat coupling reboiler is connected to the tower top gas phase outlet of the other one of the de-heavy tower and the de-light tower; the heat pump system includes a heat pump unit, a de-heavy tower heat pump reboiler arranged in the tower kettle of the de-heavy tower, and a de-light tower heat pump reboiler arranged in the tower kettle of the de-light tower; the inlet of the heat pump unit is connected to the tower top gas phase outlet of the de-light tower, the outlet of the heat pump unit is connected to the heat source inlet of the de-heavy tower heat pump reboiler, and the heat source outlet of the de-heavy tower heat pump reboiler is connected to the heat source inlet of the de-light tower heat pump reboiler. The present invention can reduce the amount of tower kettle steam and tower top cooling circulating water used in the separation process, which is economical and energy-saving.

Description

Technical Field

[0001] The present invention relates to a technology for carbon four separation. Background Art

[0002] With the continuous development of oil production and the increasingly stringent environmental protection requirements of mankind, the problems of crude oil deterioration and heaviness are becoming more and more apparent. Methyl tert-butyl ether (MTBE) is a widely used additive that can effectively improve the octane number and fuel efficiency. C4 after etherification reaction is currently mainly used as civilian liquefied petroleum gas fuel, and its chemical utilization rate is low. However, its main components butene-1, isobutane and n-butane still have high chemical utilization value. For example, butene-1 can be used as a raw material for fine chemical products such as polyethylene comonomer, methyl ethyl ketone, valeraldehyde, isodecyl alcohol, etc. Isobutane is the main source of MTBE raw material isobutene, and n-butane can also be converted into isobutane through isomerization to produce MTBE. Therefore, separating and purifying the various components in C4 helps to improve the chemical utilization rate of raw materials, extend the industrial chain, and promote the development of fine chemical industry.

[0003] At present, distillation is still the main way to separate and purify C4 hydrocarbons, and separation can be achieved based on the difference in boiling points between the components. The conventional C4 separation process uses a double-tower series operation mode, which is divided into a heavy-removal tower and a light-removal tower. The heavy-removal tower removes heavy components such as n-butane, while the light-removal tower finely separates n-butene and isobutane. However, since the components in C4 hydrocarbons have similar structures, the boiling points differ slightly, and the relative volatility is close to 1, the distillation process requires a higher number of plates and reflux ratio, and the energy consumption is very high. In conventional distillation towers, the gas phase at the top of each tower is cooled by condensed water, and the bottom of the tower is heated by steam, which requires a large amount of public works and the economic efficiency needs to be improved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a carbon four separation device and process based on differential pressure thermal coupling and heat pump distillation technology, which can reduce the consumption of tower bottom steam and tower top cooling circulating water during the carbon four separation process and reduce the energy consumption required in the separation process.

[0005] According to one aspect of an embodiment of the present invention, a carbon four separation device based on differential pressure thermal coupling and heat pump distillation technology is provided, including a distillation system and a heat pump system; the distillation system includes a de-heavy tower and a de-light tower; its characteristic is that the distillation system also includes a heat coupling reboiler, the heat coupling reboiler is arranged in the tower kettle of one of the de-heavy tower and the de-light tower, and the heat source inlet of the heat coupling reboiler is connected to the tower top gas phase outlet of the other one of the de-heavy tower and the de-light tower; the heat pump system includes a heat pump unit, a de-heavy tower heat pump reboiler arranged in the tower kettle of the de-heavy tower, and a de-light tower heat pump reboiler arranged in the tower kettle of the de-light tower; the inlet of the heat pump unit is connected to the tower top gas phase outlet of the de-light tower, the outlet of the heat pump unit is connected to the heat source inlet of the de-heavy tower heat pump reboiler, and the heat source outlet of the de-heavy tower heat pump reboiler is connected to the heat source inlet of the de-light tower heat pump reboiler.

[0006] According to another aspect of an embodiment of the present invention, a C4 separation process based on differential pressure thermal coupling and heat pump distillation technology is provided, comprising:

[0007] The C4 raw material enters the de-heavy tower, and the heavy components including n-butane are removed from the kettle of the de-heavy tower. The light component overhead gas containing isobutane and butene-1 is obtained from the top of the de-heavy tower. The light component overhead gas enters the light-removal tower, and isobutane is obtained from the top of the light-removal tower, and high-purity butene-1 is obtained from the kettle of the light-removal tower.

[0008] Part of the top gas of one of the heavy removal tower and the light removal tower enters a heat-coupled reboiler disposed in the bottom of the other one of the heavy removal tower and the light removal tower, and serves as a heat source to heat the bottom liquid;

[0009] Part of the top gas of the lightness removal tower enters the heat pump unit, and after being pressurized and heated by the heat pump unit, it enters the heat pump reboiler of the heavyness removal tower arranged in the kettle of the heavyness removal tower, and after heating the kettle liquid of the heavyness removal tower, it enters the heat pump reboiler of the lightness removal tower arranged in the kettle of the lightness removal tower, and heats the kettle liquid of the lightness removal tower in the heat pump reboiler.

[0010] The present invention has at least the following advantages and features:

[0011] 1. The temperature and pressure of the heavy removal tower and the light removal tower in C4 separation are close, and the differential pressure thermal coupling technology is used to effectively reduce the energy consumption level;

[0012] 2. Two heat pump reboilers are set in series to heat the high-temperature de-heavy tower first and then the low-temperature de-light tower. This can not only maximize the heat transfer efficiency of the tower heat pump reboiler, but also effectively supplement the heat demand of the de-light tower, achieving better energy-saving effect;

[0013] 3. Adjusting the pressure of the flash tank can match the heat demand of the system, which not only satisfies the heat of the system, but also reduces power consumption and maximizes the efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a C4 separation device based on differential pressure thermal coupling and heat pump distillation technology according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] Please refer to Figure 1 A C4 separation device based on differential pressure thermal coupling and heat pump distillation technology according to an embodiment of the present invention includes a distillation system and a heat pump system.

[0017] The distillation system includes a de-heavy tower T1, a de-light tower T2, a de-heavy tower steam reboiler E3, a de-light tower steam reboiler E4, a thermally coupled reboiler E7, a de-heavy tower top condenser E1, a de-heavy tower reflux tank V1, a de-light tower top condenser E2, and a de-light tower reflux tank V2.

[0018] The deheaving tower steam reboiler E3 is disposed in the tower bottom of the deheaving tower T1, and the deheaving tower steam reboiler E4 and the thermal coupling reboiler E7 are respectively disposed in the tower bottom of the deheaving tower T2.

[0019] The gas phase outlet of the de-weighting tower T1 is connected to the hot side inlet of the de-weighting tower top condenser E1 and the heat source inlet of the thermal coupling reboiler E7 respectively, the hot side outlet of the de-weighting tower top condenser E1 is connected to the inlet of the de-weighting tower reflux tank V1, and the liquid phase outlet of the de-weighting tower reflux tank V1 is divided into two routes: one route is connected to the top reflux port of the de-weighting tower T1, and the other route is connected to the feed port of the de-lighting tower T2. The heat source outlet of the thermal coupling reboiler E7 is connected to the hot side inlet of the de-weighting tower top condenser E1.

[0020] In this embodiment, the liquid phase outlet of the de-weighting tower reflux tank V1 is connected to the inlet of the de-weighting tower booster pump P1, and the outlet of the de-weighting tower booster pump P1 is divided into two paths: one is connected to the top reflux port of the de-weighting tower T1, and the other is connected to the feed port of the de-weighting tower T2.

[0021] The top gas phase outlet of the de-lightness tower T2 is connected to the hot side inlet of the top condenser E2 of the de-lightness tower, the hot side outlet of the top condenser E2 of the de-lightness tower is connected to the inlet of the de-lightness tower reflux tank V2, and the liquid phase outlet of the de-lightness tower reflux tank V2 is divided into two routes: one is connected to the top reflux port of the de-lightness tower T2, and the other is used for discharging.

[0022] In this embodiment, the liquid phase outlet of the lightness removal tower reflux tank V2 is connected to the inlet of the lightness removal tower booster pump P2, and the outlet of the lightness removal tower booster pump P2 is divided into two paths: one is connected to the top reflux port of the lightness removal tower T2, and the other is used for discharging.

[0023] Figure 1The portion surrounded by the dotted line frame is the heat pump system 100. The heat pump system 100 includes a heat pump unit C, a de-heavy tower heat pump reboiler E6 disposed in the tower kettle of the de-heavy tower, a light tower heat pump reboiler E5 disposed in the tower kettle of the light tower, a flash tank S and a flash tank booster pump P3.

[0024] The inlet of the heat pump unit C is connected to the top gas phase outlet of the de-lightening tower T2, the outlet of the heat pump unit C is connected to the heat source inlet of the de-lightening tower heat pump reboiler E6, the heat source outlet of the de-lightening tower heat pump reboiler E6 is connected to the heat source inlet of the de-lightening tower heat pump reboiler E5, the heat source outlet of the de-lightening tower heat pump reboiler E5 is connected to the inlet of the flash tank S, the liquid phase outlet of the flash tank S is connected to the hot side inlet of the de-lightening tower condenser E2, and the gas phase outlet of the flash tank S is connected to the inlet of the heat pump unit C.

[0025] In this embodiment, the liquid phase outlet of the flash tank S is communicated with the inlet of the flash tank booster pump P3, and the outlet of the flash tank booster pump P3 is communicated with the inlet of the heat pump unit C. The heat pump unit C includes a compressor, which is any one of the following: an oil-free twin-screw compressor, a single screw compressor, a centrifugal compressor, and a reciprocating compressor.

[0026] The aforementioned de-heavy tower T1 can be a packed tower or a plate tower, and the de-light tower T2 can be a packed tower or a plate tower. The de-heavy tower heat pump reboiler E6 and the de-light tower heat pump reboiler E5 are any of the following: falling film heat exchanger, forced circulation heat exchanger, kettle heat exchanger, plate heat exchanger, thermosyphon heat exchanger.

[0027] The steam reboiler E3 of the deheaving tower and the steam reboiler E4 of the delightening tower use external steam as a heat source to exchange heat with the liquid extracted from the tower bottom during startup and / or heat adjustment.

[0028] According to an embodiment of the present invention, a C4 separation process based on differential pressure thermal coupling and heat pump distillation technology includes:

[0029] The C4 raw material enters the de-heavy tower, and the heavy components including n-butane (mainly n-butane) are removed from the bottom of the de-heavy tower T1, and the light component top gas containing isobutane and butene-1 is obtained from the top of the de-heavy tower T1. The light component top gas enters the light-removing tower T2, and isobutane is obtained from the top of the light-removing tower T2, and high-purity butene-1 is obtained from the bottom of the light-removing tower T2;

[0030] Part of the light component tower top gas of the de-heavy tower T1 enters the heat-coupled reboiler E7 disposed in the tower bottom of the de-heavy tower T2, and is used as a heat source to heat the tower bottom liquid of the de-heavy tower T2. The tower bottom liquid of the de-heavy tower is heated and then returns to the tower bottom of the de-heavy tower T2.

[0031] Part of the top gas of the lightness removal tower T2 enters the heat pump unit C, and after being pressurized and heated by the heat pump unit C, enters the heat pump reboiler E6 of the heavyness removal tower arranged in the kettle of the heavyness removal tower, and after heating the kettle liquid of the heavyness removal tower, enters the heat pump reboiler E5 of the lightness removal tower arranged in the kettle of the lightness removal tower, and heats the kettle liquid of the lightness removal tower in the heat pump reboiler E5, and the kettle liquid of the heavyness removal tower is heated and returned to the kettle of the heavyness removal tower T1 after being heated, and the kettle liquid of the lightness removal tower is heated and returned to the kettle of the lightness removal tower T2 after being heated.

[0032] In this embodiment, the output condensate from the heat source outlet of the heat pump reboiler E5 of the lightness removal tower enters the flash tank S to recover heat, the liquid phase after flashing is pressurized by the flash tank booster pump P3 and enters the hot side inlet of the lightness removal tower condenser E2, and the gas phase after flashing enters the inlet of the heat pump unit C. In other embodiments, the output condensate from the heat source outlet of the heat pump reboiler E5 of the lightness removal tower is directly returned to the hot side inlet of the tower top condenser E2 of the lightness removal tower after being decompressed by the throttle valve.

[0033] In this embodiment, part of the light component tower top gas of the de-weighting tower T1 is condensed by the de-weighting tower top condenser E1, and then enters the de-weighting tower reflux tank V1 for gas-liquid separation, and the non-condensable gas is discharged from the top of the de-weighting tower reflux tank V1. After the condensate obtained from the de-weighting tower reflux tank V1 is pressurized by the de-weighting tower booster pump P1, a part of it is refluxed to the top of the de-weighting tower T1, and the other part enters the de-lighting tower T2 as feed. Part of the light component tower top gas of the de-weighting tower T2 is condensed by the de-weighting tower top condenser E2, and then enters the de-weighting tower reflux tank V2 for gas-liquid separation, and the non-condensable gas is discharged from the top of the de-weighting tower reflux tank V2. After the condensate obtained from the de-weighting tower reflux tank V2 is pressurized by the de-weighting tower booster pump P2, a part of it is refluxed to the top of the de-weighting tower, and the other part is discharged as the isobutylene product.

[0034] In this embodiment, the tower bottom liquid of the de-heavy tower is heated by the tower top gas of the de-heavy tower to achieve thermal coupling, which can improve the tower pressure of the de-heavy tower. In another embodiment, the heat coupling reboiler E7 is arranged in the tower bottom of the de-heavy tower T1, and the heat source inlet of the heat coupling reboiler E7 is connected to the tower top gas phase outlet of the de-heavy tower T2, and the tower top gas of the de-heavy tower T2 is used as the heating medium to heat the tower bottom liquid of the de-heavy tower T1. The tower bottom liquid of the de-heavy tower is heated by the tower top gas of the de-heavy tower to achieve thermal coupling, which can improve the tower pressure of the de-heavy tower.

[0035] In this embodiment, the C4 raw material directly enters the distillation tower. In other embodiments, the C4 raw material is preheated by the bottom product before entering the distillation tower, thereby improving energy utilization.

[0036] The following table shows the difference in total energy operating cost among conventional distillation, differential pressure thermal coupling distillation, and the differential pressure thermal coupling distillation matched with a heat pump solution of this embodiment in a specific implementation manner.

[0037]

[0038]

[0039] In the above table, the total energy operating cost is based on a steam price of 200 yuan / ton, an electricity price of 0.65 yuan / kWh, and a circulating water price of 0.1 yuan / ton.

[0040] From the table above, we can see that differential pressure thermal coupling distillation saves 40% energy compared with conventional distillation, differential pressure thermal coupling distillation with heat pump saves 67% energy compared with conventional distillation, and 46% energy compared with differential pressure thermal coupling distillation. The C4 separation device and process based on differential pressure thermal coupling and heat pump distillation technology only needs to add one set of heat pump units to achieve relatively obvious energy saving benefits.

[0041] The embodiment of the present invention utilizes a distillation process to separate and recover high value-added substances such as butene-1, normal butane and isobutane in C4, and utilizes thermal coupling and heat pump distillation technology to achieve energy saving in the distillation separation process. The two technologies are combined to achieve low-energy separation and recovery of C4. Specific application areas include but are not limited to the following industrial sites: C4 separation and recovery process in MTBE / butene-1 devices in the fields of petrochemicals and chemical industries.

Claims

1. A C4 separation device based on differential pressure thermal coupling and heat pump distillation technology, comprising a distillation system and a heat pump system; the distillation system comprises a heavy removal tower and a light removal tower; characterized in that: The distillation system further comprises a thermally coupled reboiler, which is disposed in the bottom of one of the de-heavy tower and the light-removal tower, and a heat source inlet of the thermally coupled reboiler is connected to a tower top gas phase outlet of the other one of the de-heavy tower and the light-removal tower; The heat pump system includes a heat pump unit, a de-weighting tower heat pump reboiler arranged in the kettle of the de-weighting tower, and a de-lighting tower heat pump reboiler arranged in the kettle of the de-weighting tower; the inlet of the heat pump unit is connected to the top gas phase outlet of the de-lighting tower, the outlet of the heat pump unit is connected to the heat source inlet of the de-weighting tower heat pump reboiler, and the heat source outlet of the de-weighting tower heat pump reboiler is connected to the heat source inlet of the de-lighting tower heat pump reboiler.

2. The C4 separation device according to claim 1, characterized in that: The distillation system comprises a de-weighting tower top condenser and a de-weighting tower reflux tank, the top gas phase outlet of the de-weighting tower is connected to the hot side inlet of the top condenser of the de-weighting tower, the hot side outlet of the top condenser of the de-weighting tower is connected to the inlet of the de-weighting tower reflux tank, and the liquid phase outlet of the de-weighting tower reflux tank is divided into two paths: one path is connected to the top reflux port of the de-weighting tower, and the other path is connected to the feed port of the lightness removal tower; The heat source outlet of the thermally coupled reboiler is communicated with the hot side inlet of the weight removal tower top condenser.

3. The C4 separation device according to claim 1, characterized in that: The distillation system includes a lightness removal tower top condenser and a lightness removal tower reflux tank, the top gas phase outlet of the lightness removal tower is connected to the hot side inlet of the top condenser of the lightness removal tower, the hot side outlet of the top condenser of the lightness removal tower is connected to the inlet of the lightness removal tower reflux tank, and the liquid phase outlet of the lightness removal tower reflux tank is divided into two routes: one route is connected to the top reflux port of the lightness removal tower, and the other route is used for discharging.

4. The C4 separation device according to claim 2, characterized in that: The heat pump system includes a flash tank; The heat source outlet of the heat pump reboiler of the light removal tower is connected to the inlet of the flash tank, the liquid phase outlet of the flash tank is connected to the hot side inlet of the light removal tower condenser, and the gas phase outlet of the flash tank is connected to the inlet of the heat pump unit.

5. The C4 separation device according to claim 1, characterized in that: The distillation system comprises a steam reboiler arranged in the kettle of a heavy-removal tower and a steam reboiler arranged in the kettle of a light-removal tower.

6. The C4 separation device according to claim 1, characterized in that: The heat pump unit comprises a compressor, and the compressor is any one of the following: an oil-free twin-screw compressor, a single-screw compressor, a centrifugal compressor, and a reciprocating compressor.

7. A C4 separation process based on differential pressure thermal coupling and heat pump distillation technology, characterized in that: include: The C4 raw material enters the de-heavy tower, and the heavy components including n-butane are removed from the kettle of the de-heavy tower. The light component overhead gas containing isobutane and butene-1 is obtained from the top of the de-heavy tower. The light component overhead gas enters the light-removal tower, and isobutane is obtained from the top of the light-removal tower, and high-purity butene-1 is obtained from the kettle of the light-removal tower. Part of the top gas of one of the heavy removal tower and the light removal tower enters a heat-coupled reboiler disposed in the bottom of the other one of the heavy removal tower and the light removal tower, and serves as a heat source to heat the bottom liquid; Part of the top gas of the lightness removal tower enters the heat pump unit, and after being pressurized and heated by the heat pump unit, it enters the heat pump reboiler of the heavyness removal tower arranged in the kettle of the heavyness removal tower, and after heating the kettle liquid of the heavyness removal tower, it enters the heat pump reboiler of the lightness removal tower arranged in the kettle of the lightness removal tower, and heats the kettle liquid of the lightness removal tower in the heat pump reboiler.

8. The C4 separation process according to claim 7, characterized in that: Part of the light component top gas of the de-weighting tower is condensed by the top condenser of the de-weighting tower, and then enters the reflux tank of the de-weighting tower for gas-liquid separation. The non-condensable gas is discharged from the top of the reflux tank of the de-weighting tower. After the condensate obtained from the reflux tank of the de-weighting tower is pressurized by the de-weighting tower booster pump, part of it is refluxed to the top of the de-weighting tower, and the other part enters the light-removing tower as feed.

9. The C4 separation process according to claim 7, characterized in that: Part of the light component top gas of the light component removal tower is condensed by the top condenser of the light component removal tower, and then enters the reflux tank of the light component removal tower for gas-liquid separation. The non-condensable gas is discharged from the top of the reflux tank of the light component removal tower. After the condensate obtained from the reflux tank of the light component removal tower is pressurized by the light component removal tower booster pump, part of it refluxes to the top of the light component removal tower, and the other part is discharged as isobutylene product.

10. The C4 separation process according to claim 7, characterized in that: The output condensate from the heat source outlet of the heat pump reboiler of the de-lightness tower enters the flash tank, the liquid phase after flashing is pressurized by the flash tank booster pump and enters the hot side inlet of the de-lightness tower condenser, and the gas phase after flashing enters the inlet of the heat pump unit.

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