JPS5811470B2 - Method and device for preventing coking in the upper part of a heavy oil cracking reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is applicable to the decomposition of hydrocarbons, particularly to the decomposition of heavy oils such as coal tar, shale oil (oil extracted from oil base shale), pitch, asphalt, and heavy oil.
The present invention relates to a method for preventing the upper part of a reactor from being clogged with coke-like substances and the structure of an apparatus for the same.

When a fluidized cracking system is used for heavy oil cracking, the process is generally carried out as shown in FIG.

That is, hydrocarbon oil supplied into the fluidized bed reactor 2 from the feed nozzle 1 is decomposed and converted into gaseous decomposition products and coke while passing through the fluidized bed 3 fluidized by steam or the like.

The mixture of gaseous decomposition products and steam (hereinafter referred to as "gas") enters the cyclone via the separation zone 5, entraining a portion of the fluidized particles.

Part of the fluidized particles entrained in the gas is separated in the separation zone 5, and the remainder is almost completely separated in the cyclone 6.

The gas after particle separation flows from the cyclone exit lower through the transfer pipe 8 to the device 9 for the next step.

On the other hand, the coke produced by decomposition adheres to the fluid particles,
After separating undecomposed oil etc. while passing through the stripping section 10, it is extracted from the reactor 2 and passed through the transfer pipe 11 to the regenerator 12.
and is then burned there.

In addition, particles regenerated by burning and removing adhering coke (
The regenerated particles (hereinafter referred to as "regenerated particles") are sent to the reactor 2 again through the transfer pipe 13.

However, as mentioned above, when fluidized cracking is performed using heavy oil as a raw material, there is a problem in that long-term continuous operation becomes impossible because the gas flow path in the upper part of the fluidized bed reactor, especially in the area around the cyclone, is blocked by coke-like substances. arise.

Conventionally, in order to prevent this blockage, methods have been used to control the proportion of particles entrained in the gas by adjusting the particle size of the fluidized particles or the amount of steam blown to fluidize the particles, and by reducing the inner diameter of the upper part of the fluidized bed reactor. A method has been proposed to increase the gas flow rate.

However, the former method has the problem of deviating from the optimal fluidization conditions for the reaction, and the latter method also tends to entrain heavy produced oil mist (condensation products), which is the cause of coke formation, making it more likely to become clogged. The problem is that it is difficult to solve the problem with these alone.

This invention is characterized by providing a trumpet-shaped tube that throttles the gas flow in the upper part of the fluidized bed reactor and introduces the gas into the cyclone inlet, and also maintains the temperature of the gas flow channel wall at 540 to 630°C. The present invention relates to a method for preventing coking in the upper part of a fluidized bed reactor and an apparatus therefor.

At the same time, these methods can also be applied to a general method for extracting steam from heavy oil cracking, for example, in which a subsequent pipe is directly connected to a reaction gas outlet serving as a reaction gas discharge section.

As shown in FIG. 2, the trumpet-shaped tube 22 according to the present invention is connected to the inner wall of the reactor at its lower end periphery 23, and its upper end 21 is connected to the cyclone 6 which is the reaction gas discharge part of the heavy oil cracking reactor. Connect to Cyclone Population 20.

Here, the trumpet-shaped tube partitions the conventional fluidized bed upper space 5 (FIG. 1) of the fluidized bed reactor 2 into a space 30a containing the upper surface of the fluidized bed and a space 30 above the fluidized bed reactor.

In addition, the cross-sectional area of the trumpet-like tube that crosses its axis gradually decreases as it progresses from the upper surface of the fluidized bed toward the gas discharge side, and the axis of the gas passage at the rear of the discharge side is normally turned about 90 degrees and connected to the cyclone 6. It is something.

Its external shape usually resembles the trumpet of a phonograph or the neck of a goose.

The constriction angle of the trumpet-shaped canal is θ, and the angle sign shown in the drawing is θ=α at the lower end 23 of the limb canal, and θ at the upper end 21 of the limb canal.
=β, or the way the gas flow is throttled is such that the throttle angle θ decreases from the lower end 23 to the upper end 21 so that α〉θ〉
θ〉α〉β or the aperture angle becomes sharp in the middle part
There are some that have θ〉β〉α.

Here, the aperture angle θ is defined as the curve of the tube wall surface that appears when a trumpet-shaped tube is longitudinally traversed including the axis, with the axis direction being the X axis and the radial direction orthogonal to this being the Y axis, and y = f (x). When displaying, an inflection point A is provided so that the aperture angle θ is maximized at the middle part of the trumpet-shaped tube so that the aperture angle θ is displayed.
The aperture angle θ is increased in the section from the lower end 23 to the inflection point A, and the upper end 21 is the end of the flow path with a small cross-sectional area from the inflection point A.
By decreasing the aperture angle in the section up to
The constriction angle α at the lower end 23 can be made equal to the constriction angle of the inner wall of the reactor, and the constriction angle β at the upper end 21 can be made equal to the constriction angle at the cyclone inlet, which is preferable in order to make the connection surface smooth. It is something.

In this case, the maximum value of the aperture angle θ at the inflection point A is set to 0 m.
When m, it is preferable that θmm≦90° in order to smooth the flow of gas in the trumpet-shaped tube, and θim≦
More preferably, the angle is 60°.

The gas flows upward from the upper surface 4 of the fluidized bed, and the cyclone inlet is opened horizontally, so the above-mentioned trumpet-shaped tube is inserted into the cyclone in such a way that the gas flow is restricted and the gas is introduced into the cyclone inlet. It needs to be bent.

In this case, for example, as shown in Fig. 2, it is preferable to set the gas flow path equivalent radius r/R to 0.9 or less with respect to the radius of curvature R of the trumpet-shaped tube to ensure smooth gas flow. It is more preferable to set it to .5 or less.

The surface of the wall of the trumpet-shaped pipe is made smooth using heat insulating cement (castable) or steel plate.

The method described above eliminates dead space in the upper part of the fluidized bed reactor, prevents the generation of gas vortices, and prevents the gas from stagnating for a long time, thereby eliminating reactive components or high boiling point substances in the gas. Prevents the formation and deposition of coke-like substances associated with metamorphosis.

Furthermore, by maintaining the gas flow path wall at a temperature of 540° C. to 630° C., high boiling point substances in the gas are prevented from condensing and adhering to the gas flow path wall.

Furthermore, it has been confirmed that the gas flow channel wall is preferably kept at 630°C, preferably 580°C to 540°C, in order to prevent reaction-active components or high-boiling substances in the gas from being denatured and forming a coke-like substance.

In order to maintain the temperature of the gas flow path wall as described above, a space 30 surrounded by the top of the reactor, the upper side wall of the reactor, and the trumpet-shaped tube is used as a trumpet-shaped tube wall temperature maintaining means, for example, as shown in FIG. One method is to pass a heat medium such as high-temperature steam through.

Alternatively, by blowing high-temperature particles up from a position above the top surface of the fluidized bed, the temperature of the gas flow path wall surface and the temperature of the gas itself can be increased. An example of how to increase the

In the case of FIG. 3, a blow-up tube 40 having a particle suction hole 42 is installed in the reactor fluidized bed, and the outlet of the regenerated particle transfer tube 13 is located near the particle suction hole 42. When steam is supplied from the steam nozzle 41 at the lower end of the tube, high-temperature particles are suctioned from the suction hole 42, and the suctioned particles ascend the blow-up tube 40 to an outlet 45 opened near the lower end of the trumpet-shaped tube 22a. It is blown upwards.

In addition, in the case of FIG. 4, since the particle supply port 43' is provided outside the reactor, the feature is that all or part of the high-temperature regenerated particles extracted from the regenerator can be supplied from outside the reactor fluidized bed. The supplied high temperature regenerated particles are passed through the steam nozzle 41'.
The steam blown from the pipe causes the blow-up pipe 40' to rise, and the outlet 4 opens near the lower end of the trumpet-shaped pipe 22b.
It is blown upward from 5'.

It is preferable to appropriately adjust the number of blow-up tubes or the position or direction of their exits 45, 45' according to the shape of the gas flow path in the upper part of the reactor to evenly blow up the high-temperature particles into the gas flow path.

Furthermore, by blowing up high-temperature particles along the gas flow channel wall above the upper surface of the fluidized bed, the gas flow channel wall can be efficiently and directly heated by the sensible heat of the particles.

In that case, a particle blow-up pipe as described above may be used, but as shown in FIG. 5, a distribution tank 16 is provided on the inner peripheral wall of the reactor located above the top surface of the fluidized bed, and high-temperature regenerated particles are introduced therein. The high-temperature regenerated particles can be blown up by blowing steam from the bottom of the distribution tank.

In this case, some of the high-temperature regenerated particles are extracted from the regeneration tower 12 (shown in FIG. 1) and guided by steam to the external cyclone 15'' through the transfer pipe 17'', where the high-temperature steam is separated and then introduced into the distribution tank 16. external cyclone 15
The high temperature steam separated in the space 30 can be used as a heating medium in the space 30 and then returned to the regeneration tower.

In either case, the blowing state of high-temperature regenerated particles is 0.
．． It is preferable to set the concentration within a range of 5 to 10 kg/m3 (concentration).

Further, it is appropriate that the temperature of the high-temperature recycled particles is 600 to 900°C.

By blowing up high-temperature regenerated particles as described above, it is possible to not only maintain the temperature of the gas flow channel wall at 540 to 630 degrees Celsius, but also to polish and clean the gas flow channel wall to prevent the adhesion of coke-like substances. At the same time, high-boiling substances scattered in the form of mist in the gas flow path can be combined with the blown up high-temperature regenerated particles and removed from the gas flow.

As shown in the following Examples and Comparative Examples, by using the method and its apparatus according to the present invention, it is possible to prevent coking in the upper part of the fluidized bed reaction during fluidized cracking of heavy oil, and therefore, continuous operation for a long time is possible. .

Example 1 Craate crude oil vacuum residue was subjected to the following fluid catalytic cracking treatment using a nickel oxide ore catalyst with a particle size of 70 to 400 μm.

Processing amount: 41 kg/hour Reaction temperature: 500°C Reaction pressure: 1.5 to 9/cm3 Contact time: 3.0 seconds As shown in Figure 2, the reactor is equipped with the following A tube with a trumpet-like tube shaped like this was used.

Lower end 23 cross-sectional area (reactor cross-sectional area)...697 cm3 Upper end 21 cross-sectional area (internal cyclone inlet cross-sectional area)...8 cm3 Vertical length from upper end 21 to lower end 23 8 cm R/R ratio at curved part... …………0.3 lower end 23
Aperture angle α at the upper end 21 Aperture angle β at the upper end 21 0° inflection point 22
The constriction angle θ was 50°, and the heating temperature of the gas flow path wall was 540°C.

At this time, the number of continuous operation days was 25 days.

Example 2 When carrying out the same treatment as in Example 1, the reactor had the same trumpet-shaped tube as in Example 1 at the top as shown in Figure 3, and was further equipped with the following blow-up tube for high-temperature catalyst particles. I used what I had.

Pipe diameter: 21.4mm φ Length: 1750mm Position of opening end 45: 97 vertically below the inlet of the cyclone
0 mm The high-temperature catalyst particles blown up by this pipe were as follows.

Temperature……800℃ Further, the temperature of the gas flow path wall was 560°C.

At this time, the number of continuous operation days was 30 days or more.

Comparative Example When the same treatment as in Example 1 was carried out using a conventional fluidized bed reactor as shown in Fig. 10 and keeping the gas passage wall at 485°C, The reactor was blocked by a coke-like substance and the internal pressure of the reactor increased to a dangerous state, so the operation was discontinued after three days.

Example 3 In Example 2, the amount of coke-like substance deposited within a certain period of time was investigated by changing the blow-up amount of high-temperature catalyst particles.
It became like the figure.

It is clear that if the blow-up of the high-temperature catalyst particles is set to 1 kg/m3 or more, the amount of coke-like substances deposited will be significantly reduced.

Example 4 In Example 1, when the constriction angle θmm at the inflection point A of the trumpet-shaped tube was varied and the amount of coke-like substance deposited within a certain period of time was investigated, the constriction angle θmm as shown in Fig. 7 was 90.
It is clear that the angle is preferably 60° or less.

Example 5 In Example 2, the temperature of the gas flow path wall was changed and the amount of coke-like substance deposited within a certain period of time was investigated, and the results were as shown in FIG.

It is clear that the temperature of the gas channel walls needs to be maintained between 540 and 630°C.

Although the above explanation has mainly been given by exemplifying the case where one cyclone exists in the reactor, the present invention can also be carried out even when a plurality of cyclones exist, as shown in FIG. 9 and FIG. 11, for example.

Fig. 9 is a vertical cross-sectional view of the device when there are four cyclones,
FIG. 11 shows a cross section taken along the line AA in FIG. 9.

Four cyclones 6at6 located in the fluidized bed reactor 2
As shown in FIGS. 9 and 11, bt6ct6d is located in the upper dome area a of the fluidized bed reactor 2 (hereinafter referred to as reactor 2) and is held by an arm extending from the wall of the reactor (not shown). Ru.

These cyclones are trumpet-shaped tubes 122a and 122b, respectively.
, 122c, and 122d are connected.

These trumpet-shaped tubes have a common skirt portion 122e, and together with these four trumpet-shaped tubes, partition the space above the fluidized bed of the reactor 2 into spaces 30 and 30a.

The gas discharged into the fluidized bed upper surface space 30a passes through each cyclone to separate fine solid particles such as fluidized medium particles contained therein, and returns to the fluidized bed 4. The exhaust gas is discharged into each duct 107.
a, 107b.

It passes through 107c and 107d and is discharged into the common duct 7.

A gas having a temperature of 540° C. to 630° C. is supplied from a separate device to the space 30 through a nozzle 150 to prevent the generation of coke-like substances.

The gas supplied to the space 30 is discharged from the outlet nozzle 151.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the fluidized catalytic cracking process, Figure 2 is a partial vertical cross-sectional view showing the shape of the trumpet-shaped tube installed at the top of the fluidized bed reactor, and Figures 3 and 4 are the high-temperature particle blow-up tube. Figure 5 is a vertical cross-sectional view of the device showing the shape of the device, Figure 5 is a vertical cross-sectional view of the device that implements the method of blowing high-temperature regenerated particles from the distribution tank along the inner wall of the gas flow path, and Figure 6 shows the concentration of high-temperature regenerated particles blown up. Figure 7 is a diagram showing the relationship between the amount of coke-like substance deposited, and Figure 7 is a diagram showing the relationship between the maximum constriction angle (0 mm) of the trumpet-shaped tube and the amount of coke-like substance deposited. A diagram showing the relationship between the amount of coke-like substance deposited and the temperature; FIG. 9 is a partial vertical cross-sectional view of the upper part of the device showing an example of applying the present invention when there are multiple cyclones in the reactor; FIG. FIG. 11 is a partial longitudinal cross-sectional view of the upper part of a conventional fluidized bed reactor, and is a cross-sectional view taken along the line AA in FIG. 9. DESCRIPTION OF SYMBOLS 1...Feed nozzle, 2...Fluidized bed reactor, 6...Cyclone, 12...Regenerator, 21...Upper end of truss-like tube, AA...Inflection point, 22, 22a. 22b, 22c...Tsuratsupa-shaped tube, 23...Lower end of tsuppa-shaped tube, 40, 40'...Blow-up tube, 41° 41'...Steam nozzle, 43, 43'...Particle supply port, 45,4
5'...Exit.

Claims (1)

[Scope of Claims] 1. A trumpet-shaped tube that gradually reduces the cross-sectional area of the flow path through which high-temperature gas containing solid particles is introduced is provided in the upper part of the heavy oil cracking reactor, and the end of the small cross-sectional area is connected to the reactor. It is connected to the reaction gas discharge part, and the temperature of the gas flow path wall of the trumpet-shaped tube is set to 540℃.
A method for preventing coking in the upper part of a heavy oil decomposition reactor, characterized by maintaining the temperature between ℃ and 630℃. 2. In the method according to claim 1, a cyclone on the first base is provided in the upper part of the heavy oil cracking reactor, and a trumpet-shaped tube through which the reaction gas sent from the fluidized bed flows at the inlet of each cyclone. 1. A coking prevention device for an upper part of a heavy oil decomposition reactor, characterized in that the tube wall temperature maintaining means of the trumpet-shaped tube is provided.