CN1023685C - Energy-saving process for separation of light hydrocarbons - Google Patents
Energy-saving process for separation of light hydrocarbons Download PDFInfo
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- CN1023685C CN1023685C CN92100471A CN92100471A CN1023685C CN 1023685 C CN1023685 C CN 1023685C CN 92100471 A CN92100471 A CN 92100471A CN 92100471 A CN92100471 A CN 92100471A CN 1023685 C CN1023685 C CN 1023685C
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- methane
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Abstract
The present invention provides an energy-saving technology for separating light hydrocarbons, which is characterized in that the present invention adopts the technological processes of double-tower front deethanization and low-pressure demethanization. The present invention sufficiently utilizes the characteristic of the process of low-pressure demethanization to reduce energy consumption and is suitable for the increasing production and saving reformation measures of a novel ethylene device and the existing ethylene device. The present invention can save electricity by 1350KW per hour as compared with orderly processes.
Description
The present invention relates to the separation engineering in the chemical engineering, refer more particularly to the improvement of light alkene separation process scheme in the ethylene unit, its IPC classification number is B0103/14.
Produce a kind of polycomponent mixed gas behind the well-known hydrocarbon cracking, the mixed gas after components such as overcooling and separating and cracking gasoline, Pyrolysis gas oil PGO and Pyrolysis fuel oil PFO is called lighter hydrocarbons.Lighter hydrocarbons need further processing, are separated into products such as ethene, propylene and C-4-fraction.Raw material as downstream unit.Separation process is divided into sequence flow, front-end deethanization flow process and predepropanization process according to the difference of first rectifying tower weight key ingredient.These three kinds of flow processs have different relative merits, all have been used and have built up full scale plant.Adopt 300,000 tons of/year ethylene units that have of sequence flow; Adopt 11.5 ten thousand tons of/year ethylene units that have of predepropanization process; Adopt 20,000 tons of/year gas separation units that have of front-end deethanization flow process, the synoptic diagram of these three kinds of flow processs is seen figure one, figure two and figure three.
No matter be sequence flow, front-end deethanization flow process or predepropanization process all are to adopt rectificating method to separate each component.Can notion according to the net work of sepn process, isolating energy consumption is proportional to the difference of inverse temperature at the bottom of cat head load and the cat head approximately
W
n＝QTo（ 1/(T
L) - 1/(T
H) ）
W in the formula
nThe net work consumption of-sepn process
The thermal load of Q-condenser or reboiler is proportional to the tower top outlet gas volume
T
o-envrionment temperature
T
L, T
HThe temperature of-condenser, reboiler
Use above-mentioned key concept,, can draw the relative merits of these three kinds of flow processs in conjunction with the needs of charging cooling or heating.
Adopting the purpose of sequence flow is to make the overhead product amount of each rectifying tower in the flow process minimum, thereby makes the total heat duties minimum.But because first tower is demethanizing, the service temperature of tower is minimum, and all material all will be cooled to low temperature, thereby the demethanizing tower energy consumption of sequence flow is big than other flow processs.
The design of predepropanization process is just carbon four above cuts to be separated to remove because of producing polymkeric substance at first rectifying tower to cause the root of obstruction, and helps adopting front-end hydrogenation acetylene removal technology and reduce the inventory that enters cold zone.
The total overhead product amount of front-end deethanization flow process and the temperature of first rectifying tower have been taken into account the little two kinds of requirements of mass flow that each column overhead overhead product total amount is little and advance cold zone between sequence flow and predepropanization process.
This shows that these three kinds of flow processs have different relative merits, total energy consumption is difference slightly, thinks that generally speaking the energy consumption of sequence flow is lower, thereby the large-scale ethylene plant of introducing all adopts sequence flow, but the flow process of front-end deethanization and predepropanization also can exist.The energy expenditure of the demethanizing tower of these three kinds of flow processs, deethanizing column and depropanizing tower relatively as follows:
The table literary composition is seen below
Can reach a conclusion by above-mentioned comparison: for the rectifying tower of identical cutting task, no matter be demethanizing, deethanizing or depropanizing tower, its relative energy consumption in different flow processs is all inequality, it is big to be in the relative energy input of first rectifying tower position person, this is because the charging of first rectifying tower has comprised whole hydrocarbon components, thereby load is big, and the temperature difference is big at the bottom of the cat head.If can adopt suitable flow process and processing parameter, the energy consumption that reduces first rectifying tower does not have a negative impact to other parts of flow process again, then can make the total energy consumption of this flow process be lower than other flow processs.For example, just can become the flow process that energy is saved most, purpose of the present invention that Here it is if the energy consumption of the deethanizing column in the front-end deethanization flow process is descended not to have a negative impact to other parts again.
The present invention adopts double tower front-end deethanization and low-pressure methane removing flow process, and flow process is seen Fig. 4.
The splitting gas of cracking gas compressor outlet is cooled to 0～-17 ℃ through E201, become gas-fluid two-phase mixture, in V201 gas-liquid is separated, liquid phase enters the high-pressure tower T302A of double tower deethanizing system, and gas phase further is cooled to about-37 ℃ through E202 and enters T302A again.The task of T302A is methane content to 0.02～0.09% that removes in the tower kettle product, in 0.3～0.8 ratio C-2-fraction is distributed in cat head and the tower kettle product simultaneously, overhead product enters the demethanizing chilldown system, and tower still product enters low pressure deethanizing column T302B.Carry out the clear cutting of carbon two and C3 fraction at T302B, overhead product goes to the acetylene hydrogenation system, and tower still product removes depropanizing tower.
It is integrated that T302A and demethanizing tower T301 are carried out heat, promptly by hot device with demethanizing reboiler E306 institute heat requirement as the condensation of T302A overhead gas or cool off required cold, effectively utilized heat transfer temperature difference.Enter the material of demethanizing chilldown system,, obtain 3～4 bursts of demethanizing chargings and hydrogen and low-pressure methane through progressively cooling and flash distillation.
Because the demethanizing tower charging has removed part C-2-fraction and all heavy constituent of carbon more than three, the load of demethanizing is reduced, but, the load of ethylene compressor is increased because feed component lightens, and the thermal load of charging cooling condensation moves to the low temperature direction.The present invention adopt liquid with I level separating tank and/or the outlet of II level separating tank after vacuum flashing reduces temperature and the gas of the separating tank outlet method of carrying out heat exchange reduce the load of ethylene compressor and/or methane compressor.For example, the temperature of II level separating tank is-99 ℃, and outlet liquid temperature after vacuum flashing is reduced to-115 ℃, with the gas converting heat of this liquid with-99 ℃, make gas temperature reduce to-101～-106 ℃, and the fluid temperature after the flash distillation is brought up to-106 ℃ to-110 ℃.By such heat exchange measure, though reduced the cold that the demethanizing tower reboiler reclaims, but reclaimed the cold of higher-101 ℃ and-135 ℃ of energy grade, therefore improved the grade that reclaims cold, saved the power of ethylene compressor and methane compressor.
Flow process of the present invention is applicable to newly-built ethylene unit simultaneously or has built the Increasing Production and Energy Saving transformation of device.For new device, because underlying cause makes the energy expenditure of this flow process be lower than existing sequence flow or front-end deethanization flow process.
(1) the high pressure deethanizing column adopts the multiply charging, make charging in process of cooling, not add energy in addition and just obtain several bursts of logistics that composition is inequality, and replace the clear cutting of conventional front-end deethanization flow process with the non-clear cutting of C-2-fraction, reduced the energy expenditure of deethanizing system.
(2) because the demethanizing tower charging has removed C3 fraction, the demethanizing tower bottoms can directly not remove ethylene rectification tower by deethanizing column behind acetylene hydrogenation, and ethylene concentration wherein is higher than the deethanizer overhead product, therefore both do not converge, make ethylene column form charging inequality, reduced required reflux ratio by two strands.
(3) liquid with the outlet of demethanizing charging separating tank carries out heat exchange through the gas that vacuum flashing reduces temperature and the outlet of same separating tank, has reduced the consumption of high energy position refrigerating capacity.
For producing 300000 tons of ethylene units per year, this flow process is per hour compared energy-conservation 1000KW with sequence flow.
If the ethylene unit of original employing low-pressure methane removing flow process will be extended, can make ability improve 20% with minimum investment and downtime period after adopting this flow process.Reason is:
(1) owing in time separated liquid phase in the splitting gas process of cooling, making in succession, the throughput of a series of heat exchangers has improved about 20%.
(2) double tower front-end deethanization flow process makes into that the inlet amount of demethanizing tower system has reduced 30～70%, and feed composition lightens, thereby the required quantity of reflux of demethanizing tower descends significantly, makes the demethanizing system only make minor modifications and just can increase production about 20%.
(3) drawback that the high energy position cold consumption that is caused by the front-end deethanization flow process increases is owing to adopt the method for the gas-liquid phase heat exchange of same separating tank outlet to be overcome, thereby the refrigerant condenser system only need make minor modifications and just can satisfy and increase production 20% requirement.
(4) original deethanizing column person lotus has descended about 30%, and the ethylene column load has descended 6～10%.
7. embodiment
Certain introduces 300,000 tons of ethylene units, employing order low-pressure methane removing flow process, and the splitting gas that advances separation system is composed as follows: (not counting alkynes)
(the table literary composition is seen below)
Because splitting gas is formed and original design value is variant, all at full capacity, the propylene refrigerant condenser has 5～10% affluences approximately for demethanizing tower, ethene refrigerant condenser and methane refrigerant condenser when output is 300,000 tons/year.Desire volume increase now 20%, and wish that refrigerant condenser makes an amendment less.
For the superiority of flow process of the present invention is described, compare take the most energy-conservation generally acknowledged former order flow process as benchmark, carry out whole process analog computation and the analysis of charge gas compressor outlet, it is as follows to obtain structure:
After table is seen literary composition
The superiority of learning this flow process from upper table is:
1, energy-conservation. This flow process is order flow process energy-conservation 1350kw per hour.
2, equipment changes few. Because it is constant that the cracking stock character of ethylene unit and cracking technology condition can not keep, for the elasticity that the device operation is necessary, each refrigerant condenser of design code should have certain surplus, usually 5～10%. If thereby adopt former flow process, under the condition of volume increase 20%, methane machine, ethylene machine and propylene machine all need make an amendment. And adopt flow process of the present invention, only ethylene machine makes an amendment.
Accompanying drawing and explanation thereof:
Fig. 1-sequence flow
Fig. 2-front-end deethanization flow process
Fig. 3-predepropanization process
Fig. 4-energy-saving process for separation of light hydrocarbons provided by the invention
The A-splitting gas
E201, E202, E203, E301, E302, E303, E304, E305, E306-interchanger (water cooler, condenser)
E201 in Fig. 4, E202-deethanizing feed cooler
E203-deethanizing column condenser
E301 to E305-demethanizing tower feed cooler
E306-demethanizing tower reboiler
T301-demethanizing tower (pressure 0.5-1.5KPA)
The T302-deethanizing column
T302A-high pressure deethanizing column (pressure is 2.8-4.0MPA)
T302B-low pressure deethanizing column (pressure is 1.6-2.3MPA)
The T303-depropanizing tower
Rectifying column
Domethanizing column dethanizer depropanizing tower
Flow process
The order flow process is large, medium and small
The little size of front-end deethanization flow process
Predepropanization process is medium and small big
Component H2CH
4C
2H
4C
2H
6C
3H
6C
3H
8C
4C
+ 5
mol% 17.76 24.97 37.83 5.52 10.24 0.58 2.80 0.32
Original equipment design power (KWh)＊Former flow process power demand * * flow process power demand of the present invention * *
Design load device design value (KWh) (KWh)
Methane machine 806 848 968 806
Ethylene machine 1,428 1,639 1,764 2021
Propylene machine 9,822 11,916 11,511 10068
General power 14,243 12893
Claims (1)
1, a kind of energy-conservation light hydrocarbon separating method, it is characterized in that adopting the high pressure deethanizing column of non-clear cutting to remove C3 fraction in the demethanizing tower charging, and the liquid phase that in demethanizing tower charging process of cooling the gas phase of separating tank outlet is balanced each other with it carries out heat exchange after vacuum flashing, comprises three parts:
(a) splitting gas with the cracking gas compressor outlet is cooled to 0～17 ℃, and making becomes gas-fluid two-phase mixture; After gas-liquid is separated, liquid phase enters the high-pressure tower T302A of double tower deethanizing system, and (pressure is 2.8～4.0MPa), gas phase further is cooled to about-37 ℃ and enters T302A again, the task of T302A is methane content to 0.02～0.09% that removes in the tower kettle product, in 0.3～0.8 ratio C-2-fraction is distributed in cat head and the tower still product simultaneously, overhead product enters the demethanizing chilldown system, tower still product enters low pressure deethanizing column T302B, and (pressure is 1.6～2.3MPa), carry out the clear cutting of carbon two and C3 fraction at T302B, overhead product goes to the acetylene hydrogenation system, and tower still product removes depropanizing tower;
(b) at high pressure deethanizing column (T302A, working pressure is 2.8～4.0MPa) and demethanizing tower (T301, between the pressure 0.5～1.5MPa) by interchanger with demethanizing reboiler institute heat requirement as the condensation of T302A overhead gas or cool off required cold, enter the material of demethanizing chilldown system, through progressively cooling and flash distillation, obtain 3～4 bursts of methane feed and hydrogen and low-pressure methane;
(c) adopt liquid with I level separating tank and/or the outlet of II level separating tank after vacuum flashing reduces temperature and the gas of separating tank outlet carry out the method for heat exchange to reduce the load of ethylene compressor and/or methane compressor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN92100471A CN1023685C (en) | 1992-01-29 | 1992-01-29 | Energy-saving process for separation of light hydrocarbons |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN92100471A CN1023685C (en) | 1992-01-29 | 1992-01-29 | Energy-saving process for separation of light hydrocarbons |
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| Publication Number | Publication Date |
|---|---|
| CN1063051A CN1063051A (en) | 1992-07-29 |
| CN1023685C true CN1023685C (en) | 1994-02-09 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN92100471A Expired - Fee Related CN1023685C (en) | 1992-01-29 | 1992-01-29 | Energy-saving process for separation of light hydrocarbons |
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Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1048713C (en) * | 1996-10-29 | 2000-01-26 | 倪进方 | Light hydrocarbon separation method capable of raising ethylene recovery |
| CN100551885C (en) | 2005-09-29 | 2009-10-21 | 中国石油化工集团公司 | From the product gas of preparation alkene, reclaim the method for low-carbon alkene |
| CN1911118B (en) * | 2006-08-18 | 2010-04-21 | 中国农业大学 | Kefir mushroom freeze-dried powder, production method and use thereof |
| JP6140591B2 (en) * | 2013-11-21 | 2017-05-31 | 東洋エンジニアリング株式会社 | Distillation equipment |
| CN103694072B (en) * | 2013-12-19 | 2016-04-27 | 中国石油集团东北炼化工程有限公司吉林设计院 | A kind of high-low pressure double-tower rectifying demethanizing, ethylene process |
| CN110527546B (en) * | 2018-05-24 | 2022-04-15 | 中国石油化工股份有限公司 | Method and device for reducing ethylene machine torch discharge amount of steam cracking device |
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- 1992-01-29 CN CN92100471A patent/CN1023685C/en not_active Expired - Fee Related
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| CN1063051A (en) | 1992-07-29 |
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