Method for separating n-butane and alkylate oil by low-temperature rectification process

Abstract

The invention discloses a method for separating n-butane and alkylate oil by a low-temperature rectification process, which comprises the following steps: step S1, distillation: sending an isobutane tower bottom material as a raw material to an n-butane tower for rectification, and adopting 1.6 MPa steam as a heat source at the tower bottom; step S2, separation: condensing a gas phase at the top of the n-butane tower through a condenser of the n-butane tower, and feeding the condensed gas phase into a reflux tank of the n-butane tower; step S3, condensation: pressurizing an n-butane tower reflux tank to 0.85 MPa through an n-butane tower reflux pump, then quantitatively refluxing part of the n-butane tower reflux tank, cooling part of the n-butane tower reflux tank to 40 DEG C through an n-butane cooler, then conveying the part of the n-butane tower reflux tank to a tank area, and collecting n-butane; and S4, refining: pressurizing the n-butane tower bottom material to 0.8 MPa through a product conveying pump, cooling to 40 DEG C through a cooler, conveying to a tank area, and collecting to obtain alkylated oil. According to the invention, high-purity n-butane and alkylated oil can be efficiently and continuously separated; and rectification is carried out under low-pressure and low-temperature conditions, so that the boiling point of isooctane is not reached, and n-butane with a very low boiling point can be separated out.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and particularly relates to a method for separating normal butane and alkylate by cryogenic distillation process. Background Art

[0002] In the process of petroleum refining, C4 alkylation is an important process in refinery gas processing, mainly used to produce high-octane gasoline blending components. C4 alkylation unit refers to an industrial facility that reacts isobutane and butene (or a mixture of propylene, butene, and pentene) under the action of a catalyst to produce alkylate oil mainly composed of isooctane. Alkylate oil has the characteristics of high octane number, good anti-knock performance, low vapor pressure, low sulfur content, and no olefins and aromatics. It is an ideal high-octane blending component for clean gasoline.

[0003] The alkylation process is an important oil refining process for producing high-octane gasoline components. In this process, it is necessary to separate the n-butane and alkylate oil in the reaction product to obtain high-purity alkylate oil. Therefore, a method for separating n-butane and alkylate oil by cryogenic distillation process is proposed. Summary of the invention

[0004] The object of the present invention is to provide a method for separating normal butane and alkylate by cryogenic distillation process, so as to solve the existing problems.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] The present invention is a method for separating normal butane and alkylate by cryogenic distillation process, comprising the following steps:

[0007] Step S1, distillation: the isobutane tower bottom material is sent to the normal butane tower as a raw material for distillation, and the tower bottom heat source is 1.6MPa steam;

[0008] Step S2, separation: the top gas phase of the n-butane tower is condensed by the n-butane tower condenser and then sent to the n-butane tower reflux tank;

[0009] Step S3, condensation: the n-butane tower reflux tank is pressurized to 0.85 MPa by the n-butane tower reflux pump, and part of it is quantitatively refluxed, and part of it is cooled to 40° C. by the n-butane cooler and then sent to the tank area, so as to collect n-butane;

[0010] Step S4, refining: the material at the bottom of the n-butane tower is pressurized to 0.8 MPa by a product delivery pump, cooled to 40° C. by a cooler, and then delivered to a tank area, so as to collect and obtain alkylate oil.

[0011] In one embodiment, the operating pressure of the top and bottom of the n-butane tower is 0.40-0.45 MPa, and the operating temperature is 50-164°C.

[0012] In one of the embodiments, the operating pressure of the n-butane tower reflux drum is 0.5 MPa and the operating temperature is 46°C.

[0013] In one embodiment, the n-butane tower bottom material is alkylate oil: isooctane, and the boiling point of isooctane is 98-99°C.

[0014] In one embodiment, the n-butane tower top gas phase is n-butane, and the boiling point of n-butane is -0.5°C.

[0015] In one embodiment, in step S1, the distillation is to heat the mixture to evaporate volatile components such as n-butane.

[0016] In one embodiment, the separation in step S2 is to separate the evaporated n-butane from other components by a separation device.

[0017] In one embodiment, the function of the condenser in step S3 is to condense n-butane into liquid, so as to collect pure n-butane.

[0018] In one embodiment, the refining in step S4 includes further acid washing and alkali washing of the alkylate oil to remove impurities, thereby collecting pure alkylate oil.

[0019] The present invention has the following beneficial effects:

[0020] The present invention can efficiently and continuously separate high-purity normal butane and alkylate oil, meeting the needs of the petrochemical industry.

[0021] The present invention achieves separation effect by performing rectification under low pressure and low temperature conditions; the boiling point of isooctane will not be reached, and normal butane with a very low boiling point can be separated.

[0022] The present invention can achieve effective separation while lowering the tower kettle temperature and steam consumption; isooctane does not boil, the separation effect is better, and the number of distillation tower plates can be reduced accordingly to reduce equipment costs; the pressure can adopt a slightly positive pressure to reduce the tower pressure, the tower wall thickness used in the distillation tower is reduced, and the equipment cost is reduced; the tower top reflux volume is reduced, and the steam consumption is reduced or the processing volume is increased.

[0023] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0025] Figure 1 The present invention is a flow chart of a method for separating normal butane and alkylate oil by a cryogenic distillation process. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the terms "upper", "middle", "outer", "inner" and the like indicating directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the components or elements referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] See also Figure 1 As shown, the present invention is a method for separating normal butane and alkylate by cryogenic distillation process, comprising the following steps:

[0030] Step S1, distillation: the isobutane tower bottom material is sent to the normal butane tower as a raw material for distillation, and the tower bottom heat source is 1.6MPa steam;

[0031] Step S2, separation: the top gas phase of the n-butane tower is condensed by the n-butane tower condenser and then sent to the n-butane tower reflux tank;

[0032] Step S3, condensation: the n-butane tower reflux tank is pressurized to 0.85 MPa by the n-butane tower reflux pump, and part of it is quantitatively refluxed, and part of it is cooled to 40° C. by the n-butane cooler and then sent to the tank area, so as to collect n-butane;

[0033] Step S4, refining: the material at the bottom of the n-butane tower is pressurized to 0.8 MPa by a product delivery pump, cooled to 40° C. by a cooler, and then delivered to a tank area, so as to collect and obtain alkylate oil.

[0034] Among them, the operating pressure of the top and bottom of the n-butane tower is 0.40-0.45MPa, and the operating temperature is 50-164℃.

[0035] Among them, the operating pressure of the n-butane tower reflux tank is 0.5MPa and the operating temperature is 46°C.

[0036] Among them, the bottom material of the normal butane tower is the alkylate oil: isooctane, and the boiling point of isooctane is 98-99°C.

[0037] Among them, the top gas phase of the n-butane tower is n-butane, and the boiling point of n-butane is -0.5℃.

[0038] In step S1, distillation is to heat the mixture to evaporate volatile components such as n-butane.

[0039] The separation in step S2 is to separate the evaporated n-butane from other components by using a separation device.

[0040] The function of the condenser in step S3 is to condense n-butane into liquid, so as to collect pure n-butane.

[0041] The refining in step S4 includes further acid washing and alkali washing of the alkylate oil to remove impurities, thereby collecting pure alkylate oil.

[0042] It should be further explained that the present invention achieves separation effect by performing distillation under low pressure and low temperature conditions; it does not reach the boiling point of isooctane and can separate n-butane with a very low boiling point. While achieving effective separation, first, the temperature of the tower can be reduced to reduce steam consumption; second, isooctane does not boil, the separation effect is better, and the number of distillation tower plates can be reduced accordingly to reduce equipment costs; third, the pressure can be slightly positive, the tower pressure is reduced, the tower wall thickness used in the distillation tower is reduced, and the equipment cost is reduced; fourth, the reflux amount at the top of the tower is reduced, reducing steam consumption or increasing processing volume.

[0043] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0044] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for separating normal butane and alkylate by cryogenic distillation, characterized in that: The following steps are involved: Step S1, distillation: the isobutane tower bottom material is sent to the normal butane tower as a raw material for distillation, and the tower bottom heat source is 1.6MPa steam; Step S2, separation: the top gas phase of the n-butane tower is condensed by the n-butane tower condenser and then sent to the n-butane tower reflux tank; Step S3, condensation: the n-butane tower reflux tank is pressurized to 0.85 MPa by the n-butane tower reflux pump, and part of it is quantitatively refluxed, and part of it is cooled to 40° C. by the n-butane cooler and then sent to the tank area, so as to collect n-butane; Step S4, refining: the material at the bottom of the n-butane tower is pressurized to 0.8 MPa by a product delivery pump, cooled to 40° C. by a cooler, and then delivered to a tank area, so as to collect and obtain alkylate oil.

2. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: The operating pressure of the top and bottom of the n-butane tower is 0.40-0.45 MPa, and the operating temperature is 50-164°C.

3. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: The operating pressure of the n-butane tower reflux tank is 0.5 MPa and the operating temperature is 46°C.

4. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: The bottom material of the normal butane tower is the alkylate oil: isooctane, and the boiling point of isooctane is 98-99°C.

5. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: The n-butane tower top gas phase is n-butane, and the boiling point of n-butane is -0.5°C.

6. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: In the step S1, the distillation is to heat the mixture to evaporate volatile components such as n-butane.

7. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: The separation in step S2 is to separate the evaporated normal butane from other components by using a separation device.

8. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: The function of the condenser in step S3 is to condense n-butane into liquid, so as to collect pure n-butane.

9. The method for separating normal butane and alkylate by cryogenic distillation process according to claim 1, characterized in that: The refining in step S4 includes further acid washing and alkali washing of the alkylate oil to remove impurities, thereby collecting pure alkylate oil.

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