JPS5829356B2 - Method and device for preventing coking of decomposition product transport pipes - Google Patents

Description

[Detailed Description of the Invention] This invention relates to petroleum-based hydrocarbons, particularly asphalt, heavy oil,
In a fluidized bed reactor that thermally decomposes crude oil etc. in a fluidized bed,
The present invention relates to a method for preventing coking caused by cracked products (cracked gas and cracked oil vapor) in a pipe connecting a fluidized bed reactor and a rectification section, and the structure of an apparatus used to carry out the method.

In recent years, fluidized bed reactors have been used or proposed as devices for thermally or catalytically cracking petroleum hydrocarbons such as asphalt, heavy oil, and crude oil.

In such a fluidized bed reactor, raw materials such as asphalt, heavy oil, and crude oil are fed into the fluidized bed and are thermally or catalytically cracked, and the decomposition products pass through the freeboard section, which is the space above the fluidized bed. It passes through a transfer line, which is a pipe connecting the reactor and the rectification department, and is sent to the rectification department.

In the transfer line, decomposition products or undecomposed substances become sticky liquids that adhere to the pipe walls of the transfer line (hereinafter referred to as coking), causing increased pressure loss and blockage of the pipes, which may impede the operation of the equipment. Often times a situation is reached where it is necessary to stop.

Conventionally, as measures to prevent coking in transfer lines, methods such as directly connecting a reaction device and a rectification section, cleaning with oil such as light oil or heavy oil, and using an anti-coking agent have been known.

However, the method of directly connecting the reactor outlet to the rectification section only suppresses coking by making the coking section as short as possible.

The method of cleaning with oil uses oil to dissolve the sticky liquid that causes caulking to suppress caulking, but it has the disadvantage that caulking occurs around the nozzle where the oil is blown.

The method using anti-caulking agent is at high temperature (400℃ or higher)
That doesn't have that effect.

The purpose of the present invention is to eliminate such drawbacks and to propose a method for preventing coking of a transfer line and a structure of an apparatus therefor by utilizing scattered particles scattered from a fluidized bed.

The inventors have confirmed, based on the operational results of a heavy oil pyrolysis apparatus, that the effect of removing or suppressing coking by flying particles is very effective.

The device for preventing coking according to the present invention controls the amount of scattered particles discharged to the outside of the yarn by adjusting the superficial velocity or bed height of the fluidized bed reactor, and prevents coking of the transfer line due to the scattered particles. It is something.

More specifically, the present invention has the following features.

(1) The upper part of the solid gas fluidized bed reactor is tapered with a taper angle of 200 to 120° to increase the gas velocity at the outlet of the reactor, and to A method for preventing coking of a decomposition product transport pipe, which prevents coking of a transfer line by controlling the amount of reactor outlet gas supplied to the transfer line.

(2) A method for preventing coking of a decomposition product transport pipe in which the gas flow velocity at the outlet of a fluidized bed reactor is set to 20 m/s to 150 m/s.

(3) A solid-gas fluidized bed reactor with a tapered upper structure, and a raw material supply amount control valve installed in a raw material supply pipe based on a signal from a bed height transmitter that detects the bed height of the fluidized bed. A decomposition product transport pipe comprising a layer height control device that controls a particle replenishment amount control valve provided in the particle supply pipe, and an air volume control device that controls an air volume control valve that controls the fluidizing gas supply amount based on the signal. Must be an anti-caulking device.

(4) It is a coking prevention device for a decomposition product transport pipe in which the taper angle of the conical taper part of the upper structure of the fluidized bed reactor is in the range of 200 to 1200.

The specific configuration of the present invention will be explained in more detail below based on one embodiment of the present invention.

FIG. 1 is an explanatory diagram showing the structure of an apparatus for carrying out the method of the present invention.

The nozzle 1 is for supplying raw materials such as asphalt, heavy oil, crude oil, etc., and the tower 2 is a fluidized bed reactor for thermally decomposing or catalytically decomposing the raw materials.

The transfer line 3, which is a tubular body, is for transporting the decomposition products to the rectification column of the column 4.

In such a fluidized bed reactor, decomposed products or undecomposed products coke in the transfer line 3, which is a transport pipe for the reactor, and this has been a major hindrance to continuous operation.

In this invention, by narrowing the upper structure 5 of the column 2 of the fluidized bed reactor into a tapered shape, coking removal by the amount of particles scattered from the fluidized bed reactor outlet 6 to the rectification column 4 is made more effective. This makes it easy to control the amount.

The inventors have concluded from the operation results of a heavy oil pyrolysis apparatus that the taper angle (apex angle) θ of the conical structure portion 5 is preferably 20 to 120°.

The particles sent to the rectification column 4 are precipitated in the residual oil 7 of the rectification column, and together with the residual oil 7, the slurry is passed through the slurry transport pipe 8 and returned to the fluidized bed reactor.

Furthermore, in this invention, when the height h from the perforated plate 10, which is the layer height, to the surface of the fluidized bed in the fluidized bed reactor 2 is changed, the concentration of particles in the freeboard section 2a is higher as it is closer to the surface of the fluidized bed. Therefore, the concentration of particles contained in the gas sent to the transfer line changes according to the change in the layer height h.

For this purpose, bed height detectors 13 (for example, a plurality of receivers for receiving electromagnetic waves or ultrasonic waves) are arranged in the height direction on the device wall inside the fluidized bed reaction device 2 (not shown) or on the side wall, and the opposite device wall A transmitter (not shown) is positioned at the point to generate a directional beam.

In this way, when the bed height changes and reaches the level of the selected receiver, the fluidized bed absorbs the beam at that level, and there is a difference in the beam intensity received by the receiver when the tower is empty, so the bed height can be detected. be able to.

] is installed to detect the bed height, send this as a signal to the bed height transmitter 14, and then send the signal from the bed height transmitter 14 to the raw material supply amount control valve 15, the particle replenishment amount control valve 16, and the fluidizing gas. The gas is sent to an air flow control valve 17 that controls the flow rate, indirectly detects the concentration of particles in the transfer line 3, and controls the superficial velocity and thus the gas flow rate at the outlet of the fluidized bed reactor.

Experimental results show that in order to prevent coking on the inner surface of the transfer line 3, it is best to set the gas flow rate at the outlet 6 of the fluidized bed reactor to a range of 20 to 150 m/s. and the range of the supplied gas amount to be within the range of the gas flow rate mentioned above.

Figure 2 shows an example of data obtained when the diameter of the outlet 6 of the fluidized bed reactor is 36 mm, air is used as the fluidizing gas, and silica sand consisting of an average particle size of 0.29 myx is scattered, showing a curve a. is the taper angle θ=100, and the curve is θ=20
0, curve C is θ=30°, curve d is θ=600, curve e
is θ=900, curve f is θ=120°, curve g is θ=1
800, it can be seen that the amount of scattered particles can be easily controlled when the taper angle θ of the conical upper structure portion 5 of the fluidized bed reactor is in the range of 200 to 1200.

FIG. 3 is an example of data showing the controllability of the amount of scattered particles depending on the superficial velocity of the fluidized bed reactor 2 when the taper angle θ=60°.

By implementing this invention, the supply of raw materials, bed height, and supply amount of fluidizing gas are automatically controlled, preventing coking at the outlet of the fluidized bed reactor and the transfer line, and allowing continuous operation of the device. It has various effects such as:

[Brief explanation of the drawing]

Figure 1 is a diagram showing the structure and piping of the device according to the present invention, Figure 2 is a diagram showing the relationship between the amount of scattered particles and the bed height of the fluidized bed, and Figure 3 is the relationship between the amount of scattered particles and superficial velocity. FIG. 1... Raw material supply nozzle, 2... Tower (
fluidized bed reactor), 2a... freeboard section,
3... Transfer line, 4... Rectification column, 5... Upper structure of tower 2, 6...
・Fluidized bed reactor outlet, 7...Residual oil, 8...
... Slurry transport pipe, 9 ... Raw material supply pipe,
10... Porous plate, 11... Fluidization gas transport pipe, 12... Decomposition product transport pipe, 13...
... layer height detector, 14... layer height oscillator, 1
5... Raw material supply amount control valve, 16... Particle replenishment amount control valve, 17... Air volume control valve.

Claims (1)

[Claims] 1. A reactor in which the upper part of a solid-gas fluidized bed reactor is tapered with a taper angle of 200 to 1200 to increase the gas velocity at the exit of the reactor, and to increase the bed height of the fluidized bed and supply the gas to the transfer line. 1. A method for preventing coking of a decomposition product transport pipe, characterized by preventing coking of a transfer line by controlling the amount of gas at the outlet. 2 Reactor outlet gas velocity from 20 m/s to 150 m
2. A method for preventing coking of a decomposition product transport pipe according to claim 1, characterized in that: /s. 3. A solid-gas fluidized bed reactor with a conical tapered upper structure having an apex angle of 20° to 1200°, and a raw material supply pipe installed in a raw material supply pipe based on a signal from a bed height transmitter that detects the bed height of the fluidized bed. consisting of a bed height control device that controls the supply amount control valve and the particle replenishment amount control valve provided in the particle supply pipe, and an air volume control device that controls the air volume control valve that controls the fluidizing gas supply amount based on the signal. A device for preventing coking of a decomposition product transport pipe, characterized by: