JPS5854610B2 - Method for preventing catalyst coarsening - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing coarsening of catalyst particles in a catalyst reduction process when simultaneously producing light oil and hydrogen from heavy oil.

In recent years, methods have been developed to lighten heavy oils such as atmospheric distillation residue oil and vacuum distillation residue oil by catalytic cracking. The inventors have invented a method for producing hydrogen by catalytically cracking the catalyst in the presence of hydrogen, reducing the catalyst with coke deposited on the catalyst, and then contacting the reduced catalyst with steam.

The actual operating system of this method is as shown in FIG.

That is, in FIG.
It is introduced into a fluidized bed maintained at a pressure of 5 kg/7G.

In the fluidized bed, iron (Fe) in the form of iron oxide is contained at 30 to 60%.
A granular catalyst containing a large amount of weight is fluidized by the fluidizing gas introduced through the tube 3.

Note that although steam is normally used as the fluidizing gas, decomposed exhaust gas may also be used.

In the cracking tower 2, the heavy oil is catalytically cracked by the catalyst to produce cracked oil and coke.

The lightened cracked oil is taken out from the pipe 4 in gaseous form together with the fluidizing gas.

On the other hand, coke adheres to the catalyst and is sent to the regeneration tower 6 via the transfer pipe 5.

The regeneration tower 6 is maintained at a temperature of 750 to 950°C and a pressure of 0 to 15 kg, and is supplied with air from a pipe 7.
According to the following formulas (1) to (3), part of the coke deposited on the catalyst is partially combusted to supply heat for the entire system and reduce iron oxide in the catalyst.

At this time, if the amount of coke deposited on the catalyst is insufficient to reduce the iron oxide and supply heat to the entire system, auxiliary fuel such as hydrocarbons may be directly supplied to the regeneration tower 6 for partial combustion. .

Fe2O3+C→Fe50++CO+CO2・”・”
(1) Fe3o, +C→FeO+CO+C02+m+
+ (2) FeO+C→Fe+CO+C02-(3)
Exhaust gas containing carbon dioxide and carbon monoxide produced by the reaction of iron oxide and coke and the reaction of coke and oxygen is discharged from pipe 8.

The catalyst particles heated to 750-950°C are sent to cracking tower 2 and gasification tower 11 via pipe 9 and pipe 10, respectively.

The catalyst containing reduced iron passes through a transfer pipe 10 to a gasification tower 11
There, the iron is reduced by the steam supplied from the pipe 12 as shown in formulas (4) to (5) below, and is oxidized to generate hydrogen.

The inside of the gasification tower 11 is maintained at a temperature of 600 to 800°C and a pressure of O to 15 kg/CrIF and GO.

Since the oxidation reaction of iron mainly occurs in the gasification tower 11, the hydrogen concentration in the produced gas from the gasification tower 11 taken out from the pipe 13 is extremely high, usually 80% by volume or more on a dry basis.

The oxidized catalyst is recycled to the cracking column 2 via pipe 14.

The catalyst used in the present invention is one obtained by crushing, granulating, and calcining iron-based natural ores such as laterite and siderite, or
Contains 0 to 60% by weight, with the remainder being alumina, magnesia,
It is a synthetic iron-based catalyst containing a refractory such as Shi9iki, and its particle size range is 60 to 500 μm.

In the regeneration tower in the triple circulating fluidized bed system as described above,
If the combustion heat generated by the combustion of coke or auxiliary fuel such as hydrocarbons is too high, or if the coke-adhered catalyst from the cracking tower in the previous step is circulated to the regeneration tower, or the heat is supplied from the regeneration tower to the cracking tower. This may result in long-term retention of the catalyst in the regeneration tower due to defects in the catalyst circulation for the regeneration tower or the catalyst circulation from the regeneration tower to the next step, the gasification tower, or temporary suspension of circulation of the low-temperature catalyst from the cracking tower. FeO and Fe, which have relatively low melting points, partially melt and sinter to form coarse particles due to the accompanying temperature rise in the regeneration tower and further deterioration of the local fluidization state in the fluidized bed section. hogging
It was found that this phenomenon occurs.

Coarse particles generated by this hogging make the fluidization state of the fluidized bed unstable and prevent the smooth circulation of catalyst particles.
Often caused cessation of driving.

At the very beginning of this hogging phenomenon, the bonds between the catalyst particles are weak and can be easily broken by increasing the gas flow velocity, but if this continues, it will become coarse within a short time and may cause the flow to stop. Eventually, the entire particle layer forms a strong sintered body.

Incidentally, the occurrence of such hogging in the regenerator causes a reduction in pressure loss in the fluidized bed section because a gas blowout passage is created from above the dispersion plate to the lower part of the fluidized bed when it occurs.

Therefore, by monitoring changes in pressure loss in the fluidized bed section, it is possible to know the occurrence of hogging.

The present invention provides a method for preventing catalyst particles from becoming coarse due to such hogging.

That is, the present invention uses a catalyst containing 30 to 70 to 60 by weight of iron in a fluidized state in the presence of coke and/or hydrocarbons (where 02 is insufficient to completely burn the coke and/or hydrocarbons). In this method, the coke and/or hydrocarbons are combusted under reducing conditions by bringing them into contact with a containing gas, and at the same time the catalyst is reduced, in which pressure loss in the fluidized bed section is detected and purge gas is supplied to the fluidized bed section based on the detection signal. The present invention relates to a method for preventing catalyst coarsening, which is characterized by introducing the present invention.

Regarding the introduction of purge gas, monitor the pressure loss in the fluidized bed section, and when the pressure loss starts to decrease (at the time when hogging occurs), introduce an inert purge gas such as nitrogen or regeneration tower exhaust gas into the fluidized bed section. The gas linear velocity is usually 50
The catalyst is prevented from becoming coarse by an initial measure of introducing the purge gas at a rate of at least cm/sec and stopping the introduction of the purge gas when the pressure loss has returned to its original value.

Here, the gas linear velocity in the fluidized bed section is calculated by converting the amount of gas blown into the fluidized bed section into temperature, and does not include the amount of gas generated by combustion of coke and/or hydrocarbons. .

The purge gas may be a gas that does not contain oxygen, such as nitrogen gas or regeneration tower exhaust gas, or a gas containing oxygen that generates less heat than the heat generated by combustion of coke, etc. is balanced with the heat carried away by the gas. Commonly used.

The present invention will be explained in detail below.

The role of the regeneration process in the process of producing light oil and hydrogen from heavy oil is to supply the heat obtained from the combustion of the coke deposited on the iron-containing catalyst with blown oxygen to the entire process system, as described above. However, since coke combustion takes place on the catalyst, heat dissipates more slowly than gas combustion, and the combustion heat accumulates on the catalyst particles, causing the particle surface to become localized. temperature becomes high.

On the other hand, since the iron in the catalyst is reduced by coke, the catalyst particles are placed under conditions where hogging is likely to occur.

For example, when laterite ore is used as a catalyst, the reaction temperature is 750-950°C, the superficial velocity is 15-40 cm, /
sec, catalyst residence time 10 to 30 minutes, amount of oxygen blown into the coke circulating in the fluidized bed section of the regeneration tower 0.2 to 0.5
Hogging does not occur under normal operating conditions with a molar ratio and a catalyst particle size of 0.06 to 0.4 mm, but as mentioned above, it may cause local deterioration of the fluidization state inside the fluidized bed or failure of the catalyst circulation system. hogging may occur due to

If initial hogging occurs under similar conditions, in addition to a predetermined amount of blown 02-containing gas, N2 gas, etc., is introduced as a purge gas such that the linear velocity of the fluidized bed gas is 50 crn/sec or more to temporarily eliminate the initial hogging. When the method was applied, it was found that no hogging occurred even when the iron in the catalyst was in a highly reduced state.

In addition, as described above, as a result of hogging, a gas vent passage is created in the fluidized bed section, so the pressure loss in the fluidized bed section decreases as hogging progresses.

Figure 2 shows the change in pressure loss in the fluidized bed over time when hogging occurs.At the beginning of hogging, when weak bonds between catalyst particles occur, the pressure drop gradually decreases, and then As the agglomeration becomes coarser, the pressure loss begins to decrease rapidly, and eventually all the particles in the fluidized bed become agglomerated and become sintered bodies, and hogging ends, so the pressure loss becomes constant, and at this point, the pressure loss in the fluidized bed decreases. almost disappears.

At this time, at the beginning of hogging, the bonds between the catalyst particles are weak, so if the gas linear velocity is increased to 50 crrL/sec or more, the bonds between the catalyst particles are broken as shown in Figure 3, and the pressure loss returns to normal. The progression of hogging can be prevented.

Based on the knowledge of such hogging, the present inventors have developed a method for preventing hogging by constantly monitoring and recording the pressure loss in the fluidized bed section 6 using a differential pressure transmitter 15, etc., as shown in FIGS. 4 to γ. At the same time, the center value of the pressure loss during fluctuations is 1/
Measures were taken to automatically introduce purge gas so that the gas linear velocity became 50 cIrL/see or higher when the gas velocity decreased by 20 to 1/3, preferably 1/10 to 115.

In addition, the purge gas introduction line 16 is connected to 0 as shown in FIG.
It may be connected to the 2-containing gas introduction line 7, or it may be piped directly above the dispersion plate as shown in FIG.

The piping of the purge gas introduction line directly above the dispersion plate is particularly designed to prevent hogging directly above the dispersion plate.

That is, in FIG. 5, the low temperature catalyst (54
0°C) is supplied from the catalyst transfer pipe 5 to the regenerator fluidized bed 6 along with the lift gas, but this lift gas cannot contribute to the linear velocity directly above the dispersion plate, and the linear velocity immediately above the dispersion plate is equal to the entire fluidized bed group. In addition, since the temperature lowering effect due to the supply of the low-temperature catalyst is small, hogging is particularly likely to occur directly above the distribution plate.

Therefore, as shown in Figure 6, the purge gas line 16' is piped from all sides directly above the dispersion plate, and multiple gas outlets are installed in each line so that the purge gas is blown out in all directions. By locally increasing the speed, hogging prevention directly above the dispersion plate is strengthened.

Furthermore, as shown in Fig. 7, a purge gas outlet is provided throughout the area directly below the dispersion plate, and a large amount of purge gas is locally blown out by opening and closing a valve 18 on a line branched from the purge gas line 16''. Good too.

Although not shown, in FIG. 7, the air outlet can be moved to any position directly below the dispersion plate without branching the purge gas line 16'' (for example, by making the purge gas line extractable). You can also do that.

In this way, after eliminating the initial hogging and removing the cause of hogging, such as a defect in the catalyst circulation system or an abnormally high temperature in the regeneration tower, while still introducing purge gas,
By stopping the purge gas, it is possible to return to normal operation.

As described above, the method of the present invention can prevent the occurrence of hogging and maintain a good fluidization state of catalyst particles.
Effects such as continuous operation of the heavy oil lightening process can be stably maintained.

Comparative Example A regenerator with an inner diameter of 15.1 m, a height of 1.8 m, and a fluidized bed height of 50 CIn had a bulk specific gravity of 1.72, an average particle size of 0.2 Q mm, and a composition of F34.3%, Ni 1.9%, Mg07. ．．
5%, 5i0210.0%, At2035.7%, Na
20 A laterite catalyst consisting of 1.9% (all percentages by weight) with 4.0% coke deposited was taken from a cracking tower at 11% by weight.
, 2 hold up, and air from the bottom of the regeneration tower 4.2
When the operation was carried out using a three-circuit fluidized bed system in which Nm3/h was introduced to burn coke at 950°C, reduce the catalyst, and supply the reduced catalyst to the gasification tower, it was found that within 12 minutes from the start of operation of the regeneration tower, The pressure loss in the fluidized bed section suddenly decreased, causing hogging.

Using the same equipment as in Examples and Comparative Examples, changes in pressure loss in the fluidized bed section were monitored with a differential pressure transmitter, and this electrical signal was connected to a control valve installed in the N2 gas introduction line connected to the air introduction line. At the start of operation, the control valve of the N2 gas introduction line is closed, and when the pressure loss in the fluidized bed section decreases to 1/10 of the initial pressure loss, the control valve of the N2 gas introduction line is automatically opened, and the superficial velocity force 5
It was set to 0CTL/5eC1.

When the other operating conditions were the same as in the comparative example, N2 was introduced 12 minutes after the start of operation.

After that, the temperature of the regeneration tower was lowered to 850℃, the N2 gas was stopped, and continuous operation was continued for 10 hours under the condition of 4.2Nm3/hr of air, but no decrease in pressure loss was observed and no hogging occurred. There wasn't.

In this way, if hogging is destroyed by introducing purge gas at the initial stage of hogging, normal operation can be continued simply by eliminating the cause of hogging.

[Brief explanation of drawings]

The attached Figure 1 is a flow sheet showing one embodiment of the heavy oil lightening and hydrogen production process, Figure 2 is a diagram showing changes in pressure loss due to hogging, and Figure 3 is a flow sheet showing the change in pressure loss due to the occurrence of hogging. Figure 4 shows the change in pressure loss when the temperature is 7.
FIG. 7 shows examples of various embodiments of the invention.

Claims (1)

[Claims] 1. Contacting a catalyst containing 30% by weight or more and 60% by weight or less of iron in a fluidized state in the presence of coke and/or hydrocarbons with a gas containing insufficient oxygen to completely burn the coke and/or hydrocarbons. In the method of burning the coke and/or hydrocarbons under reducing conditions and reducing the catalyst at the same time, the pressure loss in the fluidized bed section is detected, and a purge gas is introduced into the fluidized bed section based on the detection signal. A method for preventing catalyst coarsening, characterized by: