Decompression of atmospheric and vacuum distillation of the status and improvements pull

Paper Keywords: atmospheric and vacuum distillation unit pull out the vacuum system
Abstract: This paper describes the distillation unit of China Petrochemical system status and pull out the vacuum system, measures to improve the extraction rate, that heavy crude oil in the trend, raising atmospheric and vacuum distillation system, pull out the vacuum the level of play of the effectiveness of heavy crude oil.

With the tightening of supply and demand of crude oil and crude oil prices continued to rise, the procurement of crude oil refiner Sinopec increasingly heavy, caused by the partial vacuum atmospheric and vacuum distillation system overload, unclear division of wax residue, gas oil fraction lost to residue of which, has also caused the increase of the amount of residue of heavy oil refinery capacity tight and unnecessary equipment energy consumption, some enterprises are not able to sell residual oil, heavy crude oil weakened the due process efficiency. In order to ease the processing of crude oil changes heavy impact on the secondary processing equipment to improve the operation of heavy oil processing plant level, give full play to the procurement of heavy crude oil of the effectiveness of vacuum distillation unit to improve the level pull system is very important.

l Domestic vacuum distillation system, pull out the status of devices
At present, not really grasp the deep vacuum pull set of technologies, although a small number of sets of equipment from abroad, the company introduced KBC SHELL and decompression of deep drawing technology package, but the absorption of the technology will take some time to master. Generally speaking , vacuum deep drawing technology from abroad is the branch temperature reaches 420oC vacuum furnace above the boiling point of cutting the real point of crude oil reached 565 ~ 620 ��. China Petroleum and Chemical Corporation in recent years, the introduction of new technology is based on vacuum deep-drawing the real point of crude oil reached 565 �� Boiling Point cut design, that is, deep drawing technology of foreign relief starting point, the rest did not realize the depth of relief device is a device built in the main pull, asked earlier, when the boiling point of crude oil cut by more than point of 520 ~ 540 �� design, vacuum deep drawing can not be achieved.

2 of the rate of decompression systems pull factors
Vacuum tower vaporization section of vacuum pressure and temperature are two key factors pull out the depth. Steam injection tube, bottom blowing steam, feeding quantity, washing effects section also have an impact on the total extraction rate .

Vaporized by the vaporization of the pressure at the top section of the total pressure drop and top decision vacuum system operation, the higher the vacuum evaporation section, the more easily vaporized oil, vacuum pull out the depth of the higher (foreign advanced design, vaporization residue segment pressure can reach 1.33 ~ 2.00kPa). vaporization section of the temperature increase is limited by the coking furnace and high temperature thermal cracking tendency of the feed, the pressure in the evaporation under the same section in order not to form a thermal cracking to coke and premise should be to maximize the vaporization zone temperature. vaporization section of temperature, degree of oil will increase evaporation, vacuum pull out the depth increased.

3 Problems
By analyzing the system necessary to implement decompression of deep drawing operations of more than 20 sets of data decompression device of the letter stressed, pull out the device does not meet the depth of the main show the following questions.

Extraction rate of less than 3.1 atmospheric pressure system overload caused by decompression system
Most devices atmospheric distillation residue 350oC for 5% or more, up to 15%. Atmospheric residue of diesel components will increase too much load vacuum furnace, increasing the load of the vapor phase vacuum tower and increase the vacuum tower packing layer (or tray) of the pressure drop, directly affect the vacuum tower section of the vacuum evaporation.

3.2 The vacuum furnace outlet temperature of the lower evaporation rate caused by lower oil
Most pressure relief devices in order to reduce the risk of coking furnace to reduce the occurrence of thermal cracking residue, vacuum furnace temperature of multi-branch below 400 ��, vacuum tower vaporization section more in 385 �� temperature below the atmospheric residue at this temperature low level of vaporization. improve vacuum furnace outlet temperature is mainly affected by several factors constraints.

(1) tube material. Most of the vacuum furnace radiant tube device used Cr5Mo, can not adapt to mention after the furnace temperature and heat intensity, can not resist high temperature naphthenic acid corrosion, materials should be upgraded, especially the expansion of After a few tube diameter.

(2) tube hanger material. Typically, the design of vacuum tube furnace hanger material selection generally lower than the tube material needs to be upgraded to accommodate the increased temperature of the furnace after the radiation temperature.

(3) the steam injection process. Most devices have a steam injection process, but some devices do not vote in the daily operations use steam injection operations in the routine production of low refining capacity, or only as under accident conditions to prevent the coke furnace means, not to prevent a large amount of refining oil under high temperature coke. In addition, some of the steam injection point tube vacuum furnace in the feed line, the steam in the gasification furnace oil increased the total pressure drop, thereby affecting the vaporization section of the vacuum decompression. a reasonable position to be located in the steam injection flow of radiation on the furnace tube, this point of the play steam injection well within the reducing furnace oil film temperature and shorten the role of residence time reduce the oil in the furnace tube coking risk.


(4) vacuum furnace load. Some of the old device vacuum furnace tube surface heat intensity more than the design value, can not further enhance the warm deep drawing, to a substantial increase in outlet temperature vacuum furnace, vacuum furnace to be on the expansion transformation.

Paragraph 3.3 of the vacuum evaporation caused by low oil evaporation rate of less than
Part of the decompression device in the feeder section of the vacuum is low, a direct impact on the atmospheric residue in the vaporization rate and decompression systems pull out the depth. Vaporization of the main section of the vacuum by the following two restrictions.

(1) vacuum tower. The higher the vacuum tower, in a certain packing (or trays) pressure drop, the higher the feed section of the vacuum.

(2) internals, pressure drop. To improve the feed section of the vacuum tower to the key is to reduce the voltage drop between the feeder section. Internals main reasons for drop large tray and fill mix, packing more than a few paragraphs , Great packing height and diameter of decompression Tata small and large vapor phase load.

3.4 No quench oil flow and can not control the temperature raised the risk of coke after the bottom
Old equipment is not considered as the design of deep drawing operations decompression, generally do not take into account the increased temperature of the feeder section will result in bottom temperature, could easily lead pipes, heat exchangers, control valves, bottom of coke, vacuum tower bottom pump for taking the time and other effects, a lot of pressure relief device flow of quench oil is not set, can not control the temperature raised the risk of coke after the bottom and bottom cracking gas generation, long-term operation of the device and the control tower vacuum has a negative impact, Although some devices do not set specific quench oil flow, but the heat has been a vacuum residue after the vacuum tower bottom as the fuel return flow, also may help reduce the role of bottom temperature.

3.5 the nature of the oil pump seal and flow of vacuum distillate residue 5oo �� impact
Typically, the vacuum tower bottom vacuum pump oil as oil sealing the lateral line, but some still use straight-run diesel equipment for sealing oil. Straight-run diesel oil or seal oil (wax) will raise a large amount of vacuum residue in the 500 �� amount of distillate, but also may result in decompression of Tata taking the time to the end of the pump.

3.6 vacuum steam stripping tower bottom is too small or cast of the bottom of the stripping effect
Part of the unit vacuum tower has a larger load, to avoid reducing investment and vacuum tower bottom vacuum without blowing steam blowing steam or less. In addition, a small amount of devices originally designed by wet operation, in order to reduce unit production stop blowing steam energy.

Improve the extraction rate of 4 measures vacuum system
Vacuum system to improve atmospheric vacuum distillation unit is a pull-out depth of integrated engineering, we should first improve the vacuum tower design and selection of staff internals, then according to the changing nature of crude oil to adjust operating parameters to ensure safety and does not affect the plant operation period, raising severe degree of decompression operation of the system. Links to Research Papers Download http://www.hi138.com 4.1 distillation unit to improve the level of vacuum system design
(1) vacuum furnace and transfer line design of the pressure on the vaporization section have a greater impact. Using tube expander, steam injection, etc. can increase the vaporization section of temperature, increase the vaporization rate of the export furnace, transfer line temperature drop Hsiao Ke reduce oven temperature to less cracking and ensure a high extraction rate of the required temperature.

(2) using low pressure drop, high fractionation efficiency, a large flux of trays and packing, not only can improve the distillate yield and cutting precision, but also substantially increase the processing capacity of distillation tower. With all the general vacuum tower packing tower pressure drop is less than 20rnrnHg, the plate was a large vacuum drop tower, packed tower is more than twice.

(3) improve the vacuum system of the equipment level, to improve the vacuum tower. Currently steam + vacuum and hydraulic mechanical application of vacuum effects are better.

(4) decompression of the feed to improve the distribution of the structure, appropriate increase in feed inlet height above the free space can reduce the amount of entrainment.

(5) To avoid decompression bottom of coke and reduce the cracking gas generation, vacuum tower bottom of the quench oil flow should be set to control the bottom temperature does not exceed 370 ��.

(6) the design of atmospheric tower bottom to consider reducing the focus on heavy oil fractions in the previous content of 350 �� to prevent excessive atmospheric tower should be pulled out of the diesel components into the vacuum tower, resulting in partial vacuum tower at the top of the load large, high-top temperature, vacuum is low, affect the total pull rate.


4.2 improve the extraction rate of atmospheric pressure systems
Pressure relief system, deep pull pull rate on a great impact, should be based on the changing nature of crude oil atmospheric tower as much as possible to improve the pull rate and reduce the content of atmospheric residue of 350oC to 4%. Major reasonable control measures over vaporization rate and improve the atmospheric pressure furnace outlet temperature, lower atmospheric pressure on top of the tower to adjust the amount of atmospheric tower bottom and side blowing steam stripping steam lines, improving the amount of atmospheric side of the line of pull (in particular often Under the pressure of the lateral line.)
4.3 improve the vacuum furnace outlet temperature and the vacuum tower feed temperature
With the relevant tools in the case of furnace design parameters should be based on feed properties and simulation, the coking furnace curve drawn to guide the simulation results for the temperature gradually increased, even in the absence of coking furnace curve simulation software can also be increased slightly and increase the furnace temperature steam injection to observe the vacuum tower operating conditions to determine the appropriate temperature and maintain the operation, the first to reach the design temperature, on this basis to increase the steam injection tube and continue to provide temperature.

4.4 improve the vacuum degree of vacuum tower
Top taking the time to optimize the decompression device and taking the time to run cooler, reducing the system leaks taking the time to ensure that the vacuum tower.

Rational allocation of 4.5 tube and bottom blowing gas of steam injection
Reasonable distribution of the steam injection tube and bottom blowing steam flow, steam injection control the total amount of vacuum system to reduce the impact on the vacuum.

Optimization of washing operation of paragraph 4.6
To ensure that the scrubbing section to keep wetting the bottom of the fill, that spray density to guarantee a reasonable rate and the total pull out the quality of VGO, washing segment operating results, and can reduce the vaporization rate than in the same partial pressure of hydrocarbons and wax Oil quality can be improved under the premise of pull rate.

4.7 Optimization of vacuum tower to take heat distribution
To improve the extraction rate of the total device, vacuum tower can be adjusted to take heat, reduce the vacuum tower bottom of the middle back on heat to increase the vacuum tower top gas load.

4.8 vacuum tower bottom temperature control and rational
Cast by vacuum tower bottom quench oil flow, the control tower bottom temperature not exceeding 370oC can be, too much oil will affect the bottom quench the heat transfer efficiency.

Improve the extraction rate of 5 vacuum system should pay attention
(1) should be based on the processing of vacuum residue to determine the suitability of the flow of deep drawing operations, as delayed coking vacuum residue and vacuum residue feedstock for catalytic cracking, although raw material, but could not finish as well as vacuum residue catalytic digestion for fuel oil or distillation units sold outside.

(2) of crude oil boiling point cut to 565oC, the vacuum tower the lower side of the dry point line at 580oC or more must, if carried in the phenomenon will also lead to gas oil and heavy metals, asphaltene content increased, it might give hydrocracking unit caused operational problems, the proposed re-consider the implementation of deep-drawing process to re-wax, from the present into the improvement of gas oil hydrotreating hydrocracking or catalytic cracking devices.

(3) increase the depth of vacuum pulled out of the furnace exit requires high temperatures, high vacuum section of the feed, but also need to increase capacity and additional steam injection process such as quench oil, the energy consumption of the corresponding distillation unit will be increased, but From the perspective of the whole refinery, vacuum deep drawing operation of energy conservation and efficiency to achieve the dual benefits. Links http://www.hi138.com Research Papers Download