CN110590491A - Method for reducing loss of propylene at top of demethanizer prefractionator - Google Patents
Method for reducing loss of propylene at top of demethanizer prefractionator Download PDFInfo
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- CN110590491A CN110590491A CN201910836717.2A CN201910836717A CN110590491A CN 110590491 A CN110590491 A CN 110590491A CN 201910836717 A CN201910836717 A CN 201910836717A CN 110590491 A CN110590491 A CN 110590491A
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- demethanizer
- reflux
- prefractionator
- reducing
- propylene
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
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- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Water Supply & Treatment (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention belongs to the technical field of ethylene production, and particularly relates to a method for reducing the loss of propylene at the top of a demethanizer prefractionator. The method comprises the steps of reducing the opening degree of a hand valve on a return line of the demethanizer prefractionator, and reducing the gas phase quantity to reduce the return temperature; the liquid level of a reflux tank of the demethanizer pre-fractionation tower is ensured to be sufficient, and the reflux of the demethanizer pre-fractionation tower is prevented from having a gas phase; the height of the barrel of the overhead condenser of the demethanizer prefractionator and the stack height of the condenser are increased, and the reflux quantity of the demethanizer prefractionator is increased. The invention can greatly reduce the propylene content at the top of the tower to be less than 0.05mol percent, so that the propylene loss is reduced, and the coking period of the cracking furnace is prolonged.
Description
Technical Field
The invention belongs to the technical field of ethylene production, and particularly relates to a method for reducing the loss of propylene at the top of a demethanizer prefractionator.
Background
In the current ethylene generation process, ascending gas at the top of the demethanizer pre-fractionating tower is condensed by bottom effluent of the demethanizer in a tower top condenser, refrigerant flow absorbs heat and then returns to the ethylene fractionating tower under the control of a control valve, and condensed liquid returns to the top of the demethanizer pre-fractionating tower by gravity flow. The gas that is not condensed in the demethanizer prefractionator overhead condenser is sent directly to the demethanizer feed contacting column as shown in fig. 1. The main function of the demethanizing feed contact tower is to condense all the carbon three components and part of the carbon two components, thereby reducing the propylene loss at the top of the demethanizing prefractionator.
However, the main problem with the demethanizer prefractionator which is currently evident is that the overhead propylene content is 0.16 mol% (1600ppm), far exceeding the design value (<0.047 mol%, 470ppm), resulting in large propylene losses.
Disclosure of Invention
Technical problem to be solved
The invention provides a method for reducing the loss of propylene at the top of a demethanizer prefractionator, which aims to solve the technical problem of reducing the loss of propylene at the top of a tower.
(II) technical scheme
In order to solve the technical problems, the invention provides a method for reducing the loss of propylene at the top of a demethanizer prefractionator, which comprises the steps of reducing the opening of a hand valve on a reflux line of the demethanizer prefractionator, reducing the gas phase quantity and reducing the reflux temperature; the liquid level of a reflux tank of the demethanizer pre-fractionation tower is ensured to be sufficient, and the reflux of the demethanizer pre-fractionation tower is prevented from having a gas phase; the height of the barrel of the overhead condenser of the demethanizer prefractionator and the stack height of the condenser are increased, and the reflux quantity of the demethanizer prefractionator is increased.
Further, the gas phase amount is reduced by gradually reducing the hand valve on the return line to a certain opening degree, so that the return temperature is obviously reduced, and the proper hand valve opening degree is selected by analyzing the reduction amount of the propylene content on line.
Further, the gas phase quantity is reduced by reducing the opening degree of a hand valve on the return line, so that the return temperature is reduced from-38.5 ℃ before adjustment to-45 ℃ after adjustment.
Furthermore, a liquid level transmitter is added to the reflux tank, and an automatic control valve is added to a reflux line, so that the liquid level of the reflux tank is enough, and the condition that the reflux of the demethanizer pre-fractionating tower has a gas phase to influence the condensation effect of the tower is prevented.
Further, the height of the condenser cylinder is increased from 3280mm to 3400 mm; the stack height of the condenser is increased from 941mm to 1162 mm.
(III) advantageous effects
The method for reducing the loss of the propylene at the top of the demethanizer prefractionator comprises the steps of reducing the opening of a hand valve on a reflux line of the demethanizer prefractionator, reducing the gas phase quantity and reducing the reflux temperature; the liquid level of a reflux tank of the demethanizer pre-fractionation tower is ensured to be sufficient, and the reflux of the demethanizer pre-fractionation tower is prevented from having a gas phase; the height of the barrel of the overhead condenser of the demethanizer prefractionator and the stack height of the condenser are increased, and the reflux quantity of the demethanizer prefractionator is increased.
The invention can greatly reduce the propylene content at the top of the tower to be less than 0.05mol percent, so that the propylene loss is reduced, and the coking period of the cracking furnace is prolonged.
Drawings
FIG. 1 is a schematic diagram of the operation of a prior demethanizer prefractionator;
FIG. 2 is a schematic diagram of a method for reducing overhead propylene loss in a demethanizer prefractionator according to an embodiment of the present invention.
Detailed Description
In order to make the objects, contents and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.
This example provides a method for reducing the overhead propylene loss of a demethanizer prefractionator, which mainly comprises the following steps, as shown in fig. 2:
1. the reflux is a gas-liquid two-phase state proved by a higher temperature on the reflux line, the gas phase quantity is reduced by gradually closing the hand valve on the reflux line to a certain opening degree, so that the reflux temperature is obviously reduced, and the reduction of the propylene content is analyzed on line to select the proper hand valve opening degree.
The temperature before the reflux temperature is adjusted is-38.5 ℃, and the propylene content is 0.16 mol%; the adjusted temperature was-45 ℃ and the propylene content was 0.10 mol%.
2. In order to prevent the reflux of the demethanizer pre-fractionating tower from having gas phase, the invention needs to ensure that the reflux tank at the top of the demethanizer pre-fractionating tower has enough liquid level.
3. The reflux quantity of the demethanizer prefractionator is related to the liquid level of the tower top reflux tank and the height of the tower top reflux tank, when the liquid level of the tower top reflux tank is low and the height of the tower top reflux tank is insufficient, the driving force is too small, the gravity flow is discontinuous, propylene in a gas phase component at the top of the tower cannot be condensed according to a design value, the reflux of the demethanizer prefractionator is small, and the content of the propylene is ultrahigh.
Thus, this example optimizes the modification of the overhead cooler.
(1) The height of the condenser cylinder is improved: the height is increased from 3280mm to 3400 mm;
(2) increase of the stack height of the condenser: the original height is increased from 941mm to 1162 mm.
By adopting the three methods simultaneously, the reflux temperature can be continuously reduced, the reflux amount is increased, the efficiency of the tower top condenser is improved, the loss of propylene at the top of the demethanizer prefractionator of the ethylene plant is continuously reduced, and the loss is reduced from 0.16 mol% before adjustment to 0.047 mol% after adjustment.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (5)
1. A method for reducing the overhead propylene loss of a demethanizer prefractionator, comprising: the opening of a hand valve on a return line of the demethanizer pre-fractionating tower is reduced, and the gas phase quantity is reduced, so that the return temperature is reduced; the liquid level of a reflux tank of the demethanizer pre-fractionation tower is ensured to be sufficient, and the reflux of the demethanizer pre-fractionation tower is prevented from having a gas phase; the height of the barrel of the overhead condenser of the demethanizer prefractionator and the stack height of the condenser are increased, and the reflux quantity of the demethanizer prefractionator is increased.
2. The method of claim 1, wherein the amount of gas phase is reduced by gradually reducing the hand valve on the reflux line to a certain degree of opening, so that the reflux temperature is significantly lowered, and the proper degree of opening of the hand valve is selected by analyzing the amount of reduction in the propylene content on line.
3. The method of claim 2, wherein the amount of gas phase is reduced by reducing the opening of the hand valve on the return line such that the return temperature is reduced from-38.5 ℃ before adjustment to-45 ℃ after adjustment.
4. The method of claim 1, wherein a level transmitter is added to the reflux drum and an automatic control valve is added to the reflux line to ensure that the reflux drum level is sufficient to prevent the demethanizer prefractionator from refluxing with a vapor phase that could affect the condensing effect of the column.
5. The method of claim 1 wherein the condenser barrel height is increased from 3280mm to 3400 mm; the stack height of the condenser is increased from 941mm to 1162 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910836717.2A CN110590491A (en) | 2019-09-05 | 2019-09-05 | Method for reducing loss of propylene at top of demethanizer prefractionator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910836717.2A CN110590491A (en) | 2019-09-05 | 2019-09-05 | Method for reducing loss of propylene at top of demethanizer prefractionator |
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| CN110590491A true CN110590491A (en) | 2019-12-20 |
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| CN201910836717.2A Pending CN110590491A (en) | 2019-09-05 | 2019-09-05 | Method for reducing loss of propylene at top of demethanizer prefractionator |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2734237C1 (en) * | 2020-01-27 | 2020-10-13 | Андрей Владиславович Курочкин | Apparatus for complex gas treatment by low-temperature condensation |
Citations (4)
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| US20090112037A1 (en) * | 2005-07-28 | 2009-04-30 | Rian Reyneke | Process for Recovering Ethylene From an Autothermal Cracking Reactor Effluent |
| EP3241819A1 (en) * | 2016-05-02 | 2017-11-08 | Linde Aktiengesellschaft | Method for demethanizing and demethanizer |
| CN109867579A (en) * | 2017-12-01 | 2019-06-11 | 中国石化工程建设有限公司 | A kind of device and method for improving ethylene unit domethanizing column and driving to operate |
| CN109912380A (en) * | 2017-12-12 | 2019-06-21 | 中国石油化工股份有限公司 | A kind of cracking gas separation method and device |
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2019
- 2019-09-05 CN CN201910836717.2A patent/CN110590491A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090112037A1 (en) * | 2005-07-28 | 2009-04-30 | Rian Reyneke | Process for Recovering Ethylene From an Autothermal Cracking Reactor Effluent |
| EP3241819A1 (en) * | 2016-05-02 | 2017-11-08 | Linde Aktiengesellschaft | Method for demethanizing and demethanizer |
| CN109867579A (en) * | 2017-12-01 | 2019-06-11 | 中国石化工程建设有限公司 | A kind of device and method for improving ethylene unit domethanizing column and driving to operate |
| CN109912380A (en) * | 2017-12-12 | 2019-06-21 | 中国石油化工股份有限公司 | A kind of cracking gas separation method and device |
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| 丁宝苍等: "《过程控制***与装置（第二版）》", 31 August 2012, 重庆大学出版社 * |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2734237C1 (en) * | 2020-01-27 | 2020-10-13 | Андрей Владиславович Курочкин | Apparatus for complex gas treatment by low-temperature condensation |
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Application publication date: 20191220 |