CN1346689A

CN1346689A - Control method for vapour-phase linear speed compensatino of ordinary-pressure distilling tower

Info

Publication number: CN1346689A
Application number: CN 01128189
Authority: CN
Inventors: 王升亮
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-09-21
Filing date: 2001-09-21
Publication date: 2002-05-01
Anticipated expiration: 2021-09-21
Also published as: CN1140308C

Abstract

A control method for the vapor-phase linear-speed compensation of ordinary pressure distilling tower is characterized by that the over-heat vapor is introduced to the vaporizing segment of distilling tower for compensating its pressure and a set of automatic differential control meters is used to measure the pressure of rectifying segment for determining the vapor-phase linear speed variation and controlling the quantity of compensating vapor, so stabilizing the pressure gradient and temp gradient in tower and ensuring the cutting precision of crude fraction. Its advantages are high working stability of tower, and high yeild and quality of product.

Description

Control method for vapour-phase linear speed compensatino of ordinary-pressure distilling tower

The present invention relates to a kind of process control method that is used for petroleum refining processing air-distillation process.

Destilling tower vapour phase linear speed be meant crude oil be heated vapor phase product that the back generates by lighter hydrocarbons in destilling tower on the speed of ascension, be an important technology parameter in the petroleum refining process.Whether this parameter is stablized will directly influence the working condition of destilling tower, have influence on destilling tower light oil yield and fraction cutting accuracy.To at present, this " uncontrollable " parameter relatively stable usually need take various measures to make great efforts to keep in design phase, operating process in production reality for a long time.For example, need conscientiously adjust according to character, the plan treating capacity of processing crude oil, determine suitable tower diameter and tray perforation rate in the design phase, can not be excessive, again can not be too small.In operating process, to guarantee that then the raw material oil properties is identical with former design or close; Wanting strict control crude oil water content not have obviously increases; The feedstock oil flow that enters process units will keep relative stability; It is constant relatively to go into the tower oil temperature; Each capacity of returns is relatively stable.Each changes this parameter of vapour phase linear speed will be changed in above-mentioned many condition elements, influences, destroys tower internal pressure gradient and thermograde, thereby influence the rectification effect of destilling tower.Yet the temperature control device that present numerous refineries generally adopt is difficult to keep two gradients and all keeps relative stability, and tower internal pressure gradient is damaged under many circumstances, thereby can not guarantee the good operating mode of destilling tower.

The object of the present invention is to provide a kind of destilling tower vapour phase linear speed that is considered to " uncontrollable " parameter of in petroleum refining process, can controlling usually automatically, thereby strengthen the destilling tower job stability, improve the normal pressure yield, guarantee that product distillates the control method for vapour-phase linear speed compensatino of ordinary-pressure distilling tower of mouthful qualification rate.

The present invention realizes like this.This control method is to pass by vapours vaporization section pressure is compensated in atmospheric distillation tower vaporization section (or claiming feed zone) introducing one, and adopt a cover differential pressure instrument for automatic control to measure atmospheric tower rectifying section pressure and fall, the variation of falling according to pressure measures vapour phase change of line speed amount and carries out the steam compensation rate and regulate control automatically, make destilling tower vapour phase linear speed under the situation of many disturbing factor variable effects, still can keep stable, thereby stabilizer internal pressure gradient and thermograde, the stable dew-point temperature control point that respectively distillates mouth, guarantee the cutting accuracy of crude oil fraction, reach the purpose that strengthens the destilling tower job stability and improve normal pressure yield and product quality.This kind controlling party ratio juris is as follows: after tower tray or filler setting were finished, the resistance of existing tower tray or filler was just decided, and can think that this resistance is changeless.Yet its pressure falls but and will change with vapour phase rate of climb height, that is: tower tray or filling pressure fell greatly when vapour phase speed was high, otherwise then little.Thereby, record the size that pressure falls and can learn the speed of vapour phase linear speed at that time, in view of the above as seen, if can fall by steady pressure, just can stablize the vapour phase linear speed.Because the atmospheric tower top is close to normal pressure, is relative steady state value, want influence or the pressure drop of control rectifying section (that is control vapour phase linear speed), have only from changing vaporization section pressure (or claim tower at the bottom of system pressure) and start with.The present invention suitably introduces superheated steam at the destilling tower vaporization section just, make it to compensate the comprehensive vaporization rate of crude oil relative variation, make tower at the bottom of system pressure keep stable, thereby reach the purpose of control vapour phase linear speed.The implementation step and the main points of this control method are as follows:

1, determining of tower wall perforate, pipeline, control valve latus rectum.Based on compensation steam introducing amount and the proportional principle of crude runs, can adopt simple computational methods that are suitable for, promptly choose the regulating valve flow coefficient, and then select suitable control valve for use with 2 times crude runs.For example, a cover year processing capacity is the midget plant of ten thousand tons of 5--7, produces per year and days 300 days calculates, and per hour inlet amount is the 7--10 ton, can select then that rated flow coefficient is 20, the middle warm type list core control valve of latus rectum DN40 for use; If a year processing capacity is 1,000,000 tons, can select then that rated flow coefficient is 200, the control valve of latus rectum DN125 for use.So analogize, determined that the passing hole of specified control valve has just been determined the bore of pipeline and the perforate of tower wall simultaneously.At this, the relative altitude that should be noted that the perforate of tower wall should or be higher than within the horizontal level 500mm at the horizontal level of feedstock oil inlet to be chosen, and the terminal of steam pipework should be introduced the tower center, and with the elbow guiding steam is upwards blown, and prevents that along continuous straight runs from directly blowing the tower wall.

2, choosing of differential pressure transmitter measurement category and determining of instrument range.Although because destilling tower tray structure form difference causes tower tray pressure drop difference to some extent, the measurement category of differential pressure transmitter generally is chosen for 20KPa and all can satisfies the demand.Then, determine that according to actual measurement or operating position actual instrumentation range gets final product in the instrument measurement scope.

3, the type selecting of supporting instrument and meter for automation.

Select with table according to the actual operating position in our factory, so that unified supporting with original instrument model, card is regular.Homemade each series instrument of DDZ--III type or the import instrument of generally using all can satisfy instructions for use at present.

4,, vacuum distillation apparatus normal according to having now has or not primary distillation tower to determine to adopt tower outer circulation intensification start-up method or cold oil to advance the tower start-up method, when giving the destilling tower heat temperature raising, can draw the crude oil access to plant, and adjust each relevant device normal operation with compensation steam.A, can adopt tower outer circulation intensification start-up method for normal, vacuum distillation apparatus that primary distillation tower is arranged, promptly between crude oil circulation temperature raising period, do not advance atmospheric tower, but constitute the peripheral passage by the newly-increased connecting pipeline of extracting out at the bottom of the atmospheric tower behind the valve of being located at before the feedstock oil tower-entering valve; In crude oil circulation intensification, atmospheric tower heats up with compensation steam, at this moment, is used to discharge the showering guilding valve of condensed water at the bottom of need opening the Atmospheric Tower atmospheric valve and being installed in tower before the extraction valve; Between the atmospheric tower temperature raising period, to start cooling water pump, adjust each cooler water yield; Tower will be closed the cat head atmospheric valve after heating up and finishing in order, open each side line and distillate valve, close showering guilding valve at the bottom of the tower, extract valve out at the bottom of opening raw material tower-entering valve and tower, close the communicating valve on the connecting pipeline at the bottom of the tower, liquid level remains between the 40--60% at the bottom of foundation and the adjustment tower, adjusts the furnace outlet temperature and notes not overtemperature of burner hearth by concrete process chart requirement; Therefore heat exchanger does not have " thermal source " time, and the stove load is bigger, keeps heater outlet temperature so can suitably reduce inlet amount; After each side line is seen liquid level, adjust the maintenance liquid level between 40-60%; After crude oil is gone into tower, to compensation the steam preliminary before this thermograde of setting up and barometric gradient suitably adjustment a little in tower, can be normal, it is qualified to reach product; B can adopt cold oil to advance the tower start-up method for normal, the decompressor that do not have primary distillation tower, promptly heats up by connecting pipeline open circuit circulation at the bottom of the tower and heats the tank field dehydration to petroleum tank; After tower intensification work was finished, it was the same to press tower outer circulation intensification start-up method, and the switch related valve draws crude oil and goes into tower, because of oily temperature is lower, needed to keep one section open circuit recurrent state after the liquid level at the bottom of setting up tower; Suitably reduce the feedstock oil flow, adjust heating furnace and heat up, heat up by 60 ℃/h speed after heater outlet temperature reaches 250 ℃; After heater outlet temperature reaches the process chart requirement, change the open circuit circulation in good time and get rid of heavy oil or reduce pressure for the normal end.

5, the setting of vapour phase linear speed automatic regulating system and work.Automatic regulating system shows that by differential pressure transmitter, ratio, integration, differential three effects adjuster, automatic control and adjustment valve constitute a closed-loop adjustment loop.Its course of work is as follows: differential pressure transmitter records destilling tower rectifying section differential pressure value, and converts thereof into 4--20mm normalized current signal, gives indoor dish by signal conductor with this signal and adorns the measurement terminal that three effects show adjuster; After adjuster was accepted this signal, its comparing element was about to this signal and compares with artificial set-point signal, after relatively the difference result after amplifies by amplifying element, produced an output forward or backwards with ratio, integration, differential rule; This output valve is given control valve as executing agency by signal conductor, make control valve according to this output valve (order) do and drive valve accordingly or close the action of valve trend; So continuous measurement and regulation and control make measured value maintain set-point, keep destilling tower work relatively stable.

Control method for vapour-phase linear speed compensatino of ordinary-pressure distilling tower provided by the invention is novel, use this method and can realize the automatic control of destilling tower vapour phase linear speed, strengthen the stability of destilling tower work, obviously improve the fraction cutting effect, guarantee the stable raising of normal pressure yield and product quality.This method provides respond well new control measures for atmospheric tower work, uses the program that goes into operation that this technical method also can be simplified atmospheric and vacuum distillation unit, obtains good economic benefit.

Accompanying drawing is an atmospheric distillation tower vapour phase linear speed compensation controlling party provided by the invention

The method process flow diagram.

Be described further below in conjunction with the enforcement of accompanying drawing this method.

Among the figure, device parts, the components and parts apportion of each label representative are as follows:

The 1-differential pressure transmitter; 2 ₁, 2 ₂--differential pressure transmitter positive and negative pressure pressure valve; The 3--Atmospheric Tower distillates the line valve; 4--Atmospheric Tower emptying valve; 5--rectifying section tower tray; 6--instrument signal lead; 7--ratio, integration, differential (PID) three effect adjusters; 8--instrument measurement connecting pipe; 9--compensation steam automatic control and adjustment valve; 10--stripped vapor manually-operated gate; 11--superheated steam pipeline; The 12--elbow; 13--feedstock oil inlet; 14--feedstock oil tower-entering valve door; The 15--oil transfer line; The 16--communicating valve; The 17--connecting pipeline; Showering guilding valve at the bottom of the 18--atmospheric tower; Extract valve at the bottom of the 19--atmospheric tower out.

Number in the figure I, II, III are respectively rectifying section, vaporization section and the stripping section in the atmospheric distillation tower.

Claims

1, a kind of atmospheric distillation tower vapour phase linear speed control method, it is characterized in that, this method is to pass by vapours in atmospheric distillation tower vaporization section introducing one vaporization section pressure is compensated, and adopt a cover differential pressure instrument for automatic control to measure atmospheric tower rectifying section pressure and fall, the variation of falling according to pressure measures vapour phase linear speed variable quantity and carries out the steam compensation rate and regulate control automatically, it is stable that destilling tower vapour phase linear speed still can be kept under the situation of many disturbing factor variable effects, thereby stabilizer internal pressure gradient and thermograde, the stable dew-point temperature control that respectively distillates mouth, guarantee the cutting accuracy of crude oil fraction, reach the purpose that strengthens the destilling tower job stability and improve normal pressure yield and product quality; The implementation step and the main points of this control method are as follows:

1) determining of tower wall perforate, pipeline, control valve latus rectum: choose the regulating valve flow coefficient with 2 times crude runs, and then select suitable control valve for use, the latus rectum of determining control valve has also just been determined the bore of pipeline and the perforate of tower wall simultaneously;

2) choosing of differential pressure transmitter measurement category and determining of instrument range: the differential pressure transmitter measurement category can be chosen 20KPa, then the range of definite actual instrumentation in the instrument measurement scope according to actual measurement or operating position;

3) type selecting of supporting instrument and meter for automation: select with table according to the actual operating position in our factory, so that unified supporting with original instrument model, card is regular.

4) whether there is primary distillation tower to determine that atmospheric and vacuum distillation unit adopts tower outer circulation intensification start-up method or cold oil to advance the tower start-up method according to existing apparatus, when heating, heating up to destilling tower, draws the crude oil access to plant, and adjust each relevant device normal operation with compensation steam; A, can adopt tower outer circulation intensification start-up method for normal, vacuum distillation apparatus that primary distillation tower is arranged, promptly between crude oil circulation temperature raising period, do not advance atmospheric tower, but constitute the peripheral passage by the newly-increased connecting pipeline of extracting out at the bottom of the atmospheric tower behind the valve of being located at before the feedstock oil tower-entering valve; In crude oil circulation intensification, atmospheric tower heats up with compensation steam, at this moment, is used to discharge the showering guilding valve of condensed water at the bottom of need opening the Atmospheric Tower atmospheric valve and being installed in tower before the extraction valve; Between the atmospheric tower temperature raising period, to start cooling water pump, adjust each cooler water yield; Tower will be closed the cat head atmospheric valve after heating up and finishing in order, open each side line and distillate valve, close showering guilding valve at the bottom of the tower, extract valve out at the bottom of opening raw material tower-entering valve and tower, close the communicating valve on the connecting pipeline at the bottom of the tower, liquid level remains between the 40-60% at the bottom of foundation and the adjustment tower, adjusts the furnace outlet temperature and notes not overtemperature of burner hearth by concrete process chart requirement; Therefore heat exchanger does not have " thermal source " time, and the stove load is bigger, keeps heater outlet temperature so can suitably reduce inlet amount; After each side line is seen liquid level, adjust the maintenance liquid level between 40-60%; After crude oil is gone into tower, to compensation the steam preliminary before this thermograde of setting up and barometric gradient suitably adjustment a little in tower, can be normal, it is qualified to reach product; B can adopt cold oil to advance the tower start-up method for normal, the decompressor that do not have primary distillation tower, promptly heats up by connecting pipeline open circuit circulation at the bottom of the tower and heats the tank field dehydration to petroleum tank; After treating that tower intensification work is finished, it is the same to press tower outer circulation intensification start-up method, and the switch related valve draws crude oil and goes into tower, because of oily temperature is lower, needs to keep one section open circuit recurrent state after the liquid level at the bottom of setting up tower; Suitably reduce the feedstock oil flow, adjust heating furnace and heat up, heat up by 60 ℃/h speed after heater outlet temperature reaches 250 ℃; After heater outlet temperature reaches the process chart requirement, change the open circuit circulation in good time and get rid of heavy oil or reduce pressure for the normal end.

5) setting of vapour phase linear speed automatic regulating system and work: automatic regulating system shows that by differential pressure transmitter, ratio, integration, differential three effects adjuster, automatic control and adjustment valve constitute a closed-loop adjustment loop; Differential pressure transmitter converts the destilling tower rectifying section differential pressure value that records to current signal and three effects that send to show adjuster, through comparing, amplifying, outputing signal to control valve carries out, make corresponding open and close valve trend action, so continuous measurement and regulation and control, make measured value maintain set-point, keep destilling tower work relatively stable.