CN102676211B - Vacuum distillation method for improving distillate yield - Google Patents
Vacuum distillation method for improving distillate yield Download PDFInfo
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Abstract
The invention relates to a vacuum distillation method for improving distillate yield. The method comprises the steps of heating atmospheric residue to a temperature of 350-460 DEG C in a vacuum furnace; introducing the atmospheric residue to a vaporizing tower, wherein the atmospheric residue is partially vaporized in the vaporizing tower; leading out the atmospheric residue at the bottom of the vaporizing tower from the device; introducing a tower top fraction in the vaporizing tower into the vacuum distillation tower, wherein a tower top pressure of the vacuum distillation tower is 0.5-5 KPa, a tower top temperature of the vacuum distillation tower is 40-100 DEG C, and a tower bottom temperature of the vacuum distillation tower is 310-360 DEG C; and fractionating through the vacuum distillation tower to obtain heavy diesel oil and vacuum gas oil. The method employs an intermediate vaporizing tower to replace a transfer line and a vaporizing stage in the conventional atmospheric/vacuum distillation processes, and provides an individual vaporization space for oil products, so that a simple vaporization of the oil products can be realized in the vaporizing tower, energy loss caused by temperature drop and pressure drop of the transfer line can be reduced, and the distillate yield of light fraction in the vacuum distillation can be improved.
Description
Technical field
The present invention relates to a kind of method of crude oil atmospheric vacuum distillation, more particularly, relate to a kind of vacuum distillation method.
Background technology
The atmospheric and vacuum distillation of crude oil is called as refining of petroleum " tap ", and it is supplied raw materials for refinery's following process device, and directly provides portioned product.Atmospheric and vacuum distillation technology adopts " two stove three towers " flow process, i.e. primary tower, atmospheric pressure kiln, atmospheric tower, vacuum furnace and vacuum distillation tower more at present.The extracting rate that improves atmospheric distillation plant can make light constituent extract at atmospheric tower as far as possible, can not enter vacuum distillation tower again, can obtain more lighting end on the one hand, can reduce on the other hand the load of vacuum furnace and vacuum distillation tower, is conducive to energy-conservation; Improve the extracting rate of reliever, can increase the yield of distillate, for the technique such as catalytic cracking, hydrocracking provides more raw material, thereby improve the economic benefit of refinery.
The old process of air distillation process: at the bottom of the tower of primary tower, oil is heated to enter atmospheric distillation tower after part vaporization through heat exchange and atmospheric pressure kiln, at distillation tower vaporization section, light constituent is vaporized and is risen and enters distillation stage, condensation through withdrawing fluid obtains distillate from tower top or lateral line withdrawal function, the part of vaporization does not flow into stripping section downwards, on the column plate of stripping section, contact with the water vapor entering at the bottom of tower, wherein the lighting end of vaporization out and with water vapor is not upwards entered distillation stage by stripping, at the bottom of the part of vaporization does not fall into tower, draw as long residuum.
The old process of vacuum distillation process: long residuum is heated to part vaporization through vacuum furnace, enter vacuum still through transfer line, vaporize and rise at vacuum still vaporization section light constituent and enter distillation stage, after the condensation of withdrawing fluid, obtain distillate from tower top or lateral line withdrawal function, the part of vaporization is not drawn at the bottom of tower as vacuum residuum.
Analog calculation result shows, in vacuum furnace radiant coil and transfer line, the vapour phase flow velocity that is mingled with large drop is very fast, and vapour-liquid two-phase interphase mass transfer area is less, lighting end can not be vaporized completely and be wrapped in the mink cell focus of not vaporization, cause entering the actual vaporization rate of distillation tower vaporization section raw material lower than the equilibrium evaporation rate of Theoretical Calculation, a part of light component is present at the bottom of tower in residual oil, thereby reduces the extracting rate of device.Current domestic atmospheric and vacuum distillation unit generally designs vacuum residuum cut point at 540 DEG C, in much vacuum residuum, is greater than 8wt% lower than 500 DEG C of cut content, is greater than 10wt% lower than 538 DEG C of cut content, have even up to more than 30wt%.Taking Beijing Yanshan Petrochemical Company of China Petrochemical Industry refinery's atmospheric and vacuum distillation unit as example, long residuum equilibrium evaporation rate under vacuum distillation tower vaporization section temperature and pressure is 59.0wt%, and industrial extracting rate is only 51.9wt%, illustrate that industrial extracting rate and equilibrium evaporation rate still have a certain distance.As can be seen here, underpressure distillation does not reach equilibrium evaporation rate yet, and extracting rate also has very large room for promotion.
The important factor that affects atmospheric and vacuum distillation unit distillate yield is temperature and the oily vapour dividing potential drop of separation column vaporization section.Vaporization section temperature is higher, and oily vapour dividing potential drop is lower, and the vaporization rate of raw material is higher, and the extracting rate of distillate is also just higher.Improve separation column distillate yield and generally adopt the method that improves vaporization section temperature and/or reduce vaporization section pressure.Vaporization section pressure depends primarily on vacuum capability and the tower pressure drop of device, the temperature of vaporization section is subject to the impact of furnace outlet temperature: furnace outlet excess Temperature, likely there is scission reaction in heavy oil, the coke that oil product cracking generates can have a strong impact on stability and the long-term operation of device.The effect of transfer line is heated oil product to be delivered to vacuum distillation tower separate, and requires to have lower temperature drop and pressure drop, to improve vaporization section temperature and to reduce vacuum furnace pressure.The high speed transfer line pressure drop of current industrial employing is generally at 20-50kPa, and temperature drop, up to 30 DEG C, still has 10-20kPa and design good low speed pressure-reducing line for oil-transferring pressure drop, temperature drop 10-20 DEG C.The factor that affects transfer line temperature drop and pressure drop mainly contains structure design, liquid flow pattern and flow velocity etc., generally adopt the design of hole enlargement step by step, and require flow velocity can not occur plug flow, can not exceed 90% of critical flow velocity, therefore the reduction of transfer line internal drop is subject to certain limitation.
Summary of the invention
The technical problem to be solved in the present invention is the situation that does not reach equilibrium evaporation rate for vacuum distillation tower in prior art, and a kind of intensifying distillation stock oil vaporization is provided, and improves the method for atmospheric and vacuum distillation extracting rate.
A kind of vacuum distillation method that improves extracting rate provided by the invention, comprises the following steps:
Long residuum is heated to 350-460 DEG C at vacuum furnace, introduce vaporization tower, light constituent vaporization in vaporization tower, at the bottom of vaporization tower tower, residual oil is drawn from device, vaporization column overhead cut is introduced vacuum still, and vacuum still tower top pressure is 0.5-5kPa, and tower top temperature is 40-100 DEG C, column bottom temperature is 310-360 DEG C, and vacuum still fractionation obtains heavy gas oil and decompressed wax oil cut.
In method provided by the invention, claims are absolute pressure with the vacuum furnace of mentioning in specification sheets, vaporization tower and the relevant pressure of vacuum distillation tower.
In method provided by the invention, described vaporization tower operational condition is: temperature is 340-450 DEG C, preferred 390-440 DEG C, and pressure is 4-15kPa, preferred 5-10kPa.
In method provided by the invention, described vacuum furnace outlet absolute pressure 4-550kPa, vaporization tower temperature in is than the high 5-60 DEG C of vacuum distillation tower temperature in, VACUUM TOWER BOTTOM oil temperature 310-360 DEG C.
In method provided by the invention, described vacuum furnace outlet oil temperature is 350-460 DEG C, top hole pressure is 4-550kPa, with this understanding, oil product is realized part vaporization or is not vaporized completely in vacuum furnace, and ensureing has higher liquid phase fraction in boiler tube, can increase the heat transfer coefficient of oil product, also can reduce pipeline pressure drop and temperature drop, the pressure that raises in addition also helps and prevents oil product cracking and coking in boiler tube.The long residuum being heated by vacuum furnace is introduced to vaporization tower, described vaporization tower adopts simple vaporization mode, oil product is realized the vaporization of light-end products in vaporization tower, vapor-phase product wherein enters separation column through pipeline and carries out the separation of light ends oil product, vaporization bottom product directly goes out device as residual oil, no longer enter separation column, thereby shortened the residence time of residual oil in device, can effectively prevent coking.
Because separation column is simple vapour phase charging, feeding line is without adopting hole enlargement mode step by step, and structure is more simple.Separation column only carries out fractionation to vaporization tower vaporised fraction, and service temperature reduces, and tower top and lateral line discharging are heavy gas oil and each side line wax oil, are heavy wax oil at the bottom of tower, and its purposes can be adjusted as required flexibly.
In method provided by the invention, described vaporization tower also can adopt atomization strengthening vaporization mode, and described atomization strengthening can adopt spray atomization, utilizes nozzle that oil product is atomized into fine drop particle, and droplet completes the fast vaporizing of light constituent in vaporization tower.
In method provided by the invention, described vaporization tower can adopt dry type operation or wet type operation.When vaporization tower adopts dry type operation, 2-5 layer herringbone baffle plate is set at the bottom of tower, and the anti-stifled filler of high-throughput is set, preferably grid class filler, porosity is greater than 95%, specific surface 20-100m
2/ m
3, to increase the heat exchange surface of oil product, the light constituent of wherein carrying secretly is vaporized as far as possible, reduce light constituent content in residual oil; Vaporization tower adopts wet type when operation, at the bottom of vaporization tower tower, 4-8 piece column plate is set, and open ratio of plate 5-15% introduces stripped vapor in addition at the bottom of tower, thereby the tower that makes to vaporize has the function of separation column stripping stage concurrently, and quantity of steam is the 0.1-2wt% of load at the bottom of vaporization tower tower.
In method provided by the invention, according to product property and needs, preferably in described vaporization column overhead, scum dredger is set, wire mesh demister falls in preferred lower pressure, to reduce the entrainment in vapour phase, improves the quality of light ends oil product.At described vaporization tower vapour phase discharge port, steam injector is set and injects Quick steam, to reduce vaporization tower working pressure, improve vaporization rate, injecting steam amount is the 0.1-2wt% of tower top load.
In method provided by the invention, described vaporization tower diameter is 0.6-1.5 times of vacuum still diameter.At the bottom of tower, adopt undergauge design, make the residual oil residence time be less than 6 minutes.Cause coking for preventing at the bottom of tower that oil temperature is too high, also can at the bottom of vaporization tower, squeeze into quenching oil, oil temperature at the bottom of tower is down to below 360 DEG C.
In air distillation process, for improving the extracting rate of atmospheric distillation tower, vaporization tower provided by the invention can also be set before atmospheric distillation tower, for improving atmospheric distillation tower extracting rate.
Compared with prior art, the beneficial effect of vacuum distillation method provided by the invention is:
(1) replace transfer line and the separation column vaporization section in existing normal decompression technique with middle vaporization tower, for oil product provides an independent vaporization space, in vaporization tower, can realize the simple vaporization of oil product, the power loss of bringing because of transfer line temperature drop and pressure drop can be reduced, and the extracting rate of underpressure distillation lighting end can be improved;
(2) residual oil directly shifts to an earlier date extraction at the bottom of vaporization tower, can shorten residual oil and leave the residence time after process furnace;
(3) vapor-phase product of vaporization tower enters separation column through transfer line and carries out the separation of light ends oil production, and owing to having removed double distilled segmentation, separation column can operate at lower temperature.
Brief description of the drawings
Fig. 1 is the schematic flow sheet of vacuum distillation method provided by the invention;
Fig. 2 is the strengthening vaporization mode schematic flow sheet of vacuum distillation method provided by the invention.
Embodiment
Below in conjunction with accompanying drawing, vacuum distillation method provided by the invention is further described, but not thereby limiting the invention.
The schematic flow sheet that accompanying drawing 1 is vacuum distillation method provided by the invention.As shown in Figure 1, treat that the stock oil (long residuum) of fractionation is squeezed into preheating in process furnace 2 through fresh feed pump 1, process furnace 2 outlet of still pressure are 4-550kPa, and furnace tubing temperature out is 350-460 DEG C.Stock oil after preheating is introduced in vaporization tower 3, fully vaporization in vaporization tower 3, the gas phase fraction after vaporization is introduced in vacuum still 4 and is continued to separate, the liquid phase component obtaining after vaporization as residual oil from caterpillar at the bottom of vaporization tower tower.
Fig. 2 is the schematic flow sheet of the another kind of embodiment of vacuum distillation method provided by the invention, different with Fig. 1 is, long residuum through vacuum furnace heating is small droplets by atomising unit atomization, spray in vaporization tower, because droplet has great specific surface area, vaporizable cut fully vaporization within the extremely short time in vaporization section droplet moving process.
Comparative example
Comparative example 1 illustrates the effect of conventional vacuum distillation method of the prior art.
350 DEG C of long residuums are heated to 385 DEG C of tower temperature ins through vacuum furnace, wherein transfer line temperature drop is 21 DEG C, pressure drop is 37kPa, vacuum distillation tower vaporization section pressure is 5.5kPa, process furnace load is 235MJ/t raw material, Top of Vacuum Tower pressure is 1.6kPa, and vacuum distillation tower adopts dry type operation, does not play quenching oil to compare at the bottom of tower.Under this operational condition, vacuum distillation tower tower top temperature is 78 DEG C, and column bottom temperature is 388 DEG C, establishes three lateral line dischargings, and vacuum residuum yield is 55wt%, and 500 DEG C (TBP), taking front-end volatiles as 7.3wt%, it is 537 DEG C that decompressed wax oil is done.
Embodiment 1
Embodiment 1 explanation the invention provides to the effect of vacuum distillation method.
Flow process as shown in Figure 1,350 DEG C of long residuums enter vacuum furnace 2 after pump 1 supercharging, be heated to enter after 395 DEG C of tower temperature ins in the middle of vaporization tower 3, described vaporization tower tower diameter is 1.2 times of vacuum distillation tower tower diameter, at the bottom of vaporization tower tower, is 6 blocks of solid valve type column plates, and open ratio of plate is 8%, tower top is equipped with wire mesh demister, vaporization pressure tower is 8kPa, and process furnace load is 228MJ/t raw material, and furnace outlet to the tower temperature drop of vaporizing is 8 DEG C.In vaporization tower, light constituent flashes to vapour phase and enters vacuum distillation tower 4 and carry out the separation of reduced pressure distillate oil product, and Top of Vacuum Tower pressure is 1.7kPa, 71 DEG C of tower top temperatures, and 330 DEG C of column bottom temperatures, establish three lateral line dischargings, and it is 554 DEG C that VACUUM TOWER BOTTOM heavy wax oil is done; Liquid-phase product as vacuum residuum directly from vaporization tower at the bottom of extraction, 391 DEG C of extraction temperature, vacuum residuum yield is that 51%, 500 DEG C (TBP) is taking front-end volatiles as 6.5wt%.
Embodiment 2
Embodiment 2 explanation the invention provides to the effect of vacuum distillation method vaporescence in atomization strengthening vaporization tower.
Flow process is as shown in Figure 2: 350 DEG C of long residuums enter vacuum furnace 2 after pump 1 supercharging, be heated to enter after 430 DEG C of tower temperature ins in the middle of vaporization tower 3 complete atomization and vaporescence, described vaporization tower tower diameter is 0.8 times of vacuum distillation tower tower diameter, at the bottom of vaporization tower tower, it is high-throughput grid class filler, packed height is 1.2m, tower top is equipped with wire mesh demister, before vaporization tower entrance, pressure is 500kPa, process furnace load is 233MJ/t raw material, furnace outlet, to vaporizing 4 DEG C of tower temperature drops, adopts spraying plant that long residuum is sprayed in vaporization tower.Vaporization top of tower vapor phase exit steam injector injecting steam, steam injection amount is the 0.5wt% of tower top vapour phase discharging, vaporization pressure tower 6kPa.396 DEG C of vacuum residuum extraction temperature, yield is that 45%, 500 DEG C (TBP) is taking front-end volatiles as 4.2wt%; Top of Vacuum Tower pressure is 2.5kPa, and tower top temperature is 74 DEG C, and column bottom temperature is 350 DEG C, establishes three lateral line dischargings, and it is 572 DEG C that VACUUM TOWER BOTTOM heavy wax oil is done.
From embodiment and comparative example, in the situation that process furnace load is substantially suitable, adopt the vacuum residuum yield obtaining in embodiment of the method 1 provided by the invention to reduce by 4 percentage points compared with comparative example, correspondingly underpressure distillation extracting rate has improved 4 percentage points; What the atomization enhancement method that embodiment 2 adopts obtained subtracts slag yield is only 45%, 10 percentage points are reduced compared with comparative example, its underpressure distillation extracting rate has improved 10 percentage points, in sum, illustrates that vacuum distillation method provided by the invention is conducive to improve the extracting rate of stock oil.
Claims (8)
1. one kind is improved the vacuum distillation method of extracting rate, it is characterized in that, long residuum is heated to 350-460 DEG C at vacuum furnace, introduces vaporization tower, part vaporization in vaporization tower, at the bottom of vaporization tower tower, residual oil is drawn from device, vaporization column overhead cut is introduced vacuum still, and vacuum still tower top pressure is 0.5-5kPa, and tower top temperature is 40-100 DEG C, column bottom temperature is 310-360 DEG C, and vacuum still fractionation obtains heavy gas oil and decompressed wax oil cut.
2. according to the method for claim 1, it is characterized in that, described vaporization tower temperature is 340-450 DEG C, and pressure is 4-15kPa.
3. according to the method for claim 2, it is characterized in that, described vaporization tower temperature is 390-440 DEG C, and pressure is 5-10kPa.
4. according to the method for claim 1 or 2, it is characterized in that, at the bottom of described vaporization tower tower, high-throughput filler or column plate are set.
5. according to the method for claim 1 or 2, it is characterized in that, described vaporization tower arranges steam injector, and quantity of steam is the 0.1-2wt% of tower top load.
6. according to the method for claim 1 or 2, it is characterized in that, introduce air lift steam at the bottom of described vaporization tower tower, quantity of steam is the 0.1-2wt% of load at the bottom of tower.
7. according to the method for claim 1 or 2, it is characterized in that, described vaporization column overhead arranges wire mesh demister.
8. according to the method for claim 1, it is characterized in that, described vaporization tower diameter is 0.6-1.5 times of vacuum still diameter.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101376068A (en) * | 2008-09-17 | 2009-03-04 | 天津大学 | Atmospheric vacuum distillation method and apparatus with vacuum flash vaporizer |
| CN101717658A (en) * | 2009-12-03 | 2010-06-02 | 中国石油天然气集团公司 | Multi-vaporization feeding method of oil product fractionator |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101376068A (en) * | 2008-09-17 | 2009-03-04 | 天津大学 | Atmospheric vacuum distillation method and apparatus with vacuum flash vaporizer |
| CN101717658A (en) * | 2009-12-03 | 2010-06-02 | 中国石油天然气集团公司 | Multi-vaporization feeding method of oil product fractionator |
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