JPH04322747A - Method and device for removing substance such as carbon substance from particles containing said substance - Google Patents

Abstract

PURPOSE: To lower the height of a first riser type reaction column by separating a solid and gas at the top of the first reaction column, introducing separated particles into the upper part of a second fluidized bed type reaction column, introducing an oxygen-contg. gas into the lower part, taking the processed particles out of the lower part of the reaction column and recirculating part thereof to the lower part of the riser type reaction column. CONSTITUTION: The particles contg. carbonaceous materials are introduced into the lower part of the first riser type reaction column 1 and the oxygen-contg. gas is introduced from a pipe 3 into the lower part thereof. The column 1 is operated at the temp. suitable for burning off the carbonaceous materials under entraining conditions having a relatively high density phase in the lower part and a relatively low density phase in the upper part. The solid and the gas are separated in the top of the column 1. The separated particles are introduced into the upper part of the second fluidized bed type reaction column 8 and the oxygen- contg. gas is introduced from a pipe 9 into the lower part of the column 8. The column 8 is operated at the temp. suitable for burning off the carbonaceous materials under the fluidized bed conditions. The processed particles are taken out of the lower part of the column 8 and are partly recirculated via a pipe 11 to the lower part of the column 1.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to a method and apparatus for removing carbonaceous materials from particles containing such materials.

0002

BACKGROUND OF THE INVENTION Fluid catalytic cracking (FCC) processes are used to convert relatively heavy hydrocarbon products obtained from the processing of crude oil into lighter hydrocarbon products. The catalyst particles used in these processes become contaminated with carbonaceous material very quickly. These carbonaceous materials must be removed in a regeneration step to enable the catalyst particles to be reused. To regenerate the catalyst, the catalyst is contacted with an oxygen-containing gas in a fluidized bed at a temperature suitable to burn off the carbonaceous material, thereby restoring the activity of the catalyst. In this specification, unless otherwise specified, reactor refers to a regeneration reactor.

[0003] A suitable FCC charging material is 250-290°C.
, especially light oil boiling in the range of 370 to 540°C. However, there is now a trend toward using heavier feedstocks, such as atmospheric and vacuum retentate oils, which are often mixed with light oils. Since these residual oil charges usually contain significant amounts of asphaltenes which are highly susceptible to coke formation during cracking operations, more coke is deposited on the catalyst. This is especially the case when only residual oil charges are used without mixing with lighter gas oil fractions. When regenerating these spent catalyst particles with heavy coke build-up, it can be difficult to burn off enough coke to provide a suitably low concentration of carbon on the regenerated catalyst. To overcome these difficulties, regeneration towers have been proposed that burn coke to carbon monoxide, thereby limiting the heat generated in the regeneration tower. Carbon monoxide can be used as a fuel gas, for example to produce electricity or water vapor. Alternatively, a carbon monoxide boiler may be included after the regeneration tower for complete combustion of the carbon monoxide to carbon dioxide.

A method and apparatus for regenerating FCC spent catalyst particles by burning off carbon with the production of carbon monoxide is described in US Pat. No. 4,260,475. The first stage of this regeneration process consists of an entrained bed of catalyst particles moving upward in the same direction as the regeneration gas.
The reaction is carried out in a riser-type reactor using an ined bed. The second stage of regeneration is carried out in a multistage fluidized bed of catalyst particles moving countercurrently and eventually downwardly to the regeneration gas. The method of the above-mentioned US patent, as described in the specification, has several advantages that clearly make it superior to other known regeneration methods.

[0005]

A disadvantage of the process described in the above-mentioned US patent is that the riser reactor must have an extremely high height in order to obtain a reasonable removal of carbonaceous components in the first stage. It must not happen. This is because the temperature of the spent catalyst particles is initially too low for rapid combustion. Optimal performance of the catalytic cracking process is obtained when the starting reaction mixture of hydrocarbons and catalyst particles at the lower end of the riser cracking reactor has a temperature of 520 to 560°C. During the cracking step in the riser cracking reactor, the temperature drops to 20° to 30°C due to the endothermic nature of the reaction, resulting in a temperature of the spent catalyst particles of 490° to 540°C. During normal stripping of the catalyst the temperature is further reduced by 5°C. Therefore, the spent catalyst particles introduced into the riser regeneration reactor are normally at 485 to 535°C.
has a temperature of This temperature is too low to efficiently burn out the carbonaceous components deposited on the catalyst particles during the cracking process. Efficient combustion occurs at temperatures above 650°C. Combustion can therefore take place at a reasonable rate - thanks to exothermic oxidation - before a sufficiently high temperature is achieved, leaving the slowly oxidizing mixture of spent catalyst and oxygen
It must be transported over long distances in the riser regeneration reactor. As a result, extremely tall riser regeneration reactors are required, increasing construction costs and requiring large residual quantities of catalyst, resulting in high material, maintenance, and operating costs for the equipment.

[0006]

[Means for solving the problem] Particles containing a carbonaceous substance are introduced into the lower part of a first riser type reaction tower, and an oxygen-containing gas is introduced into the lower part, and a relatively high density phase is formed in the lower part. The reaction column is operated under entrainment conditions with a relatively low density phase at the top and at a temperature suitable to burn off the carbonaceous material, resulting in the separation of solids and gases at the top of the reaction column. The particles are introduced into the upper part of the second fluidized bed reaction column, while the oxygen-containing gas is introduced into the lower part of the second reaction column, and the reaction is carried out under fluidized bed conditions at a temperature suitable to burn off the carbonaceous material. by operating the column, removing the treated particles from the bottom of the reaction column, and recycling a portion of the treated particles to the bottom of the riser type reaction column.
It has now been discovered that the drawbacks of the aforementioned methods of removing particles containing carbonaceous material can be overcome.

The process uses a substoichiometric amount or an excess of oxygen-containing gas to react one or both of the reactants in such a way that the flue gas at the top of the reaction column is substantially oxygen-free. It can be operated by feeding the tower. In the method described above, the drawbacks of prior art methods are overcome. By circulating the regenerated catalyst particles from the second reaction column to the first reaction column, an increase in temperature of the particles occurs in the first reaction column. As a result, and due to the fact that the lower part of the first reaction column is operated with a relatively high density phase - and therefore with a long residence time compared to a relatively low density phase, a significant portion of the carbonaceous component is It is already burned off at the bottom of the reaction tower. Therefore, the height of the riser type reaction tower can be returned to a more practical height.

[0008] In processes which operate by feeding less than stoichiometric amounts of oxygen-containing gas to the first reactor or both reactors, the regenerated catalyst particles are removed from the second reactor. Recirculation to the first reaction column is particularly advantageous as it compensates for limited heat generation in the first reaction column.

Owing to the fact that the operation of the second reaction column is not influenced, at least within some limits, by the operation of the first reaction column, this system has great flexibility and therefore the circulating particles It is observed that the amount of can be varied over a wide range. This is especially the case when the residual amount of particles in the second reaction column is relatively high compared to the first reaction column. The ratio between the amount of particles withdrawn from the second reaction column and the amount of particles reintroduced into the first reaction column is between 0.1 and 10, and preferably between 0.2 and 5, more preferably between 0. It can vary from 3 to 1. The recycled particles must be introduced into the relatively dense phase of the first reaction column. The recycled particles may be withdrawn at various heights via one or more outlets of the second reaction column.

The process of the invention is particularly suitable for the regeneration of FCC spent catalyst particles, although it can also be used for other processes, such as the combustion of retorted oil shale particles. The amount of carbon on the FCC spent catalyst particles is suitably from 0.5 to 4% by weight, preferably from 0.3 to 1.5% by weight. The particles are introduced into the relatively dense phase of the first reaction column.

[0011] The process of the present invention preferably comprises a first reaction column containing 5
25°C to 725°C, preferably 550 to 650°C
°C and in the second reaction column at a temperature of 625 to 950 °C, preferably 700 to 800 °C. The substoichiometric amount of oxygen introduced into the first reaction column is between 20 and 70%, and preferably between 40 and 60%, most preferably between It can be 50%. The pressure in both reaction columns is suitably between 1 and 10 bar, preferably between 1.5 and 4 bar. The pressure drop across the first reaction column is suitably between 0.1 and 2 bar, preferably 0.
．． 3 to 1 bar. The pressure drop across the second reaction column is suitably between 1 and 5 bar, preferably between 1.5 and 4 bar.

The second reaction column to be used in the process of the invention is preferably a multistage fluidized bed. As mentioned above, the method of the present invention is particularly suitable for regenerating FCC spent catalyst particles. The feedstock for the FCC process is preferably a hydrocarbon fraction boiling between 250 and 590°C, especially between 370 and 540°C. Preferred feedstocks are atmospheric and vacuum residual fractions and so-called synthetic feedstocks, such as kerosene, bitumen, shale oils and their high-boiling fractions. Usually the boiling range is 250 to 600°C, or higher, and preferably a substantial amount boils above 450°C. Conversion conditions are from about 425°C to about 6
25°C, preferably in the range of about 510°C to about 610°C. Decomposition conditions also preferably include pressures ranging from about atmospheric pressure to about 4 atmospheres or more, particularly preferably from about 2 atmospheres to about 3 atmospheres. In decomposition using a fluidized bed of individual particles, from about 2 to about 5
A catalyst/hydrocarbon weight ratio of 0, preferably from about 3 to about 10 is usually quite suitable. A weight hourly space velocity of about 5 to about 50 weight hydrocarbons/hour is preferably used in the cracking operation.

The cracking zone used may be of conventional design and includes dilute-phase solid contact between the hydrocarbon charge and the catalyst particles.
fluidized solids contact
t), riser-type entrained solid contact (riser-type
entrained solids cont.
act), dense-bed solid contact
fluidized solids contact)
, countercurrent contact, moving beds of solids, packed beds or combinations thereof can be used. Gases such as water vapor or nitrogen may assist in fluidizing, entraining, etc. the catalyst. Customary stripping means of such solids can also be suitably used to remove volatile components from exhausted solids.

The solid consisting of individual particles to be used in the cracking process optionally has catalytic activity or can serve simply as a heat carrier and a sorbent for the hydrocarbons. Essentially, the particulate solids used are preferably abrasion resistant and heat resistant to the high temperatures and steaming characteristic of the process, so as to be able to be circulated in a fluidized system for a practical period of time. There must be. Customary particulate cracking catalysts and heat transfer solids can be used in this process. Suitable cracking catalysts can include crystalline zeolite aluminosilicate components.

Particulate solids other than the active acidic decomposition catalyst are
Instead of or in addition to the above, it may also be recycled in the decomposition system. For example, alumina particles can be included in the particulate solids residue to control sulfur oxides, and/or particles containing highly active combustion promoting metals, such as Group VIII noble metals, can be incorporated into catalyst or thermal carrier particles. May be mixed with Similarly, particles with heat-carrying capacity but low inherent acidic decomposition activity may be circulated alone or in admixture with a more active and acidic decomposition catalyst;
Heat may be supplied for acidic decomposition or essentially thermal decomposition of hydrocarbons. According to the invention, the coke-containing particles resulting from the cracking of hydrocarbons are produced in two stages, namely (
Regeneration is performed in: 1) an entrained bed stage in which the particles and regeneration gas move in a co-directional upward flow; and (2) a fluidized bed stage in which the particles and regeneration gas move in a generally countercurrent flow.

[0016] The first regeneration zone, in which the particles are partially regenerated in an entrained flow in an upwardly moving gas, is preferably regenerated upwardly at the temperature and pressure used in the first regeneration stage. It may be delimited by any vessel, conduit, reaction column or the like capable of containing the moving gases and solids. Riser-type vessels or transfer line vessels of the type conventionally used when performing riser-cracking in fluidized catalytic cracking systems are suitable for use as the first regeneration zone of the process. The vessel or conduit used to provide the riser-type regeneration zone contains the desired gas and the like to create a relatively high density phase at the bottom of the zone and a relatively low density phase at the top of the zone. It can be sized in length and cross-sectional area to provide solid flow rates and residence times. A preferred method of creating a density difference is to introduce a sufficient amount of gas at a certain height or to reduce the cross-sectional area to increase the velocity of the gas. If the cross-sectional area is relatively small, the cross-sectional area of the higher density phase zone is suitably 4 to 100 times, preferably 5 to 50 times, more preferably 9 times the cross-sectional area of the lower density phase zone. ~25 times larger.

Preferably, the riser reactor column is equipped with means for introducing molecular oxygen into the entrained gas stream at a plurality of vertically spaced levels in the first regeneration zone. A second regeneration zone in which the fluidized particles move generally downward in countercurrent to the upwardly moving gas also includes fluidized particles in the flowing gas at the temperature and pressure used in the second flow stage of regeneration. The scope may be defined by any vessel, conduit, reaction column, or the like that can be used. Preferably, the second regeneration zone is formed from a vertically extending vessel having a length and diameter suitably adjusted to provide gas and solids residence times and solids fluidization according to the parameters of the method. Become. In order to prevent a total back-mixing of the particles moving generally downwards in the second regeneration zone, the vessels used may be equipped with barriers, baffles, solid or gas dispersion means, redistribution means or the like. Some means must be provided to prevent such back-mixing. For example, perforated plates, rods, wire mesh, fillers, or other suitable internals may be used to prevent back-mixing.
ernal) can be used.

In addition to the desired amount of molecular oxygen, the introduced catalyst entrainment-regeneration gas can include relatively inert gases such as nitrogen, water vapor, carbon monoxide, carbon dioxide, and the like. The composition of the entrained gas, of course, varies along the gas flow path through the regeneration zone as the gas passes from the upward flow end to the downward flow end of the riser reactor column. The amount of entrained gas in the riser and its pressure and surface velocity are:
Particles present in the riser are maintained at a size such that they are entrained upwardly through the riser.

The residence time of the solids in the relatively low density phase zone of the riser reactor of about 3 to 6 seconds and about 2
Gas residence times of between 4 seconds and 4 seconds are generally suitable. Preferably, when the entrained gas is recovered from the riser reactor, it has a sufficiently high fuel value to have utility as a fuel gas. The utility of the effluent gas from the riser reactor as a fuel gas depends primarily on the carbon monoxide content of the gas. This can be varied by the partial pressures of oxygen and water vapor, total pressure, residence time of gases and solids, and the appropriate temperature maintained in the riser reactor column. Either the desired amount of coke can be burned off in the entrained bed reactor to introduce all the oxygen into the downward flow end of the reactor or some oxygen can be introduced further along the entrained gas path in the first stage. Preferably, the amount of molecular oxygen (free oxygen) introduced into the regeneration zone of the stage is controlled. The entrained gas leaving the first regeneration zone is generally 0
．． It has an oxygen concentration of 5% by volume or less. Preferably, the effluent gas contains no more than 0.1% by volume of molecular oxygen. If it is desired to operate a riser type reactor to obtain a flue gas of high fuel value, the first and second reactor towers preferably have separate flue systems.

After withdrawing the partially regenerated particles from the riser reactor and separating them from the entrained gas stream, the particles move downward in generally countercurrent fashion to the fluidizing gas stream. It undergoes a second regeneration stage in a fluidized bed. In performing the second regeneration stage, the particles are passed through the upper end of a generally vertically extending regeneration zone where the particles are fluidized by an upwardly flowing gas stream. The coke-free regenerated particles are withdrawn from the lower end of the regeneration zone for reintroduction into the cracking process, and a portion thereof is recycled to the first reaction column.

The present invention also relates to an apparatus for removing carbonaceous materials from particles containing such materials. For this, solid inlet means (2) are used in the lower part of the reaction column.
and a gas inlet means (3), usually vertical;
a first riser-type reaction tower (1) consisting of an elongated reaction tower;
Means (4) for separating solids and gases, having an inlet (5) connected to the upper part of the first reaction column and having a gas outlet (6) and a solids outlet (7); / a normally vertical reaction column connected to the solids outlet (7) of the solids separation means and provided with gas inlet means (9) and solids outlet means (10) in the lower part of the reaction column; a second fluidized-bed reaction column (8) consisting of Reference is made to FIG. 1, which represents the apparatus of the invention in conjunction with a column.

In a preferred embodiment, the lower part of the riser reactor has a larger diameter than the upper part of the reactor, as shown in FIG. Further details regarding this feature are provided above. A conical reaction column can also be used. In another preferred embodiment one or more additional gas inlet means (
12) exists. Preferably, the solids outlet means of the gas/solids separation means is connected to the upper part of the second reaction column. Preferably one or more cyclones may be used. The solids discharge means of the second reaction column is preferably located in the lower part of the reaction column. The second fluidized bed reactor is preferably equipped with an internal (13) which makes it possible to create a multistage fluidized bed. Plates, gauges, trays, etc. can be used. The solids recirculation means are preferably provided with valves allowing adjustment of the recirculation ratio. The second reaction column may be provided at its upper part with an outlet for the separated gas or may be connected to a gas/solids separation as described in European Patent Application No. 0206399, for example. It may be integrated with the gas outlet of the means. The second reaction tower may be provided with heat exchange means, for example, at the bottom of the reaction tower. Preferably, for example European Patent Application No. 3
As described in No. 40852, a heat exchanger for cooling is provided at the bottom of the reaction column.

[Brief explanation of the drawing]

FIG. 1 is an elevational view showing the configuration of the device of the present invention.

[Explanation of symbols]

1 Riser type reaction tower 2 Solid inlet means 3 Gas inlet means 4 Means for separating solid and gas 6
Gas outlet 7 Solid outlet 8 Fluidized bed reaction tower 9 Gas inlet means 10 Solid outlet means

Claims (15)

[Claims] Claim 1: Particles containing carbonaceous material are introduced into the lower part of a first riser-type reaction tower, and an oxygen-containing gas is introduced into the lower part, and the lower part has a relatively high density phase, and operating the reaction column under entrainment conditions with a relatively low density phase at the top and at a temperature suitable to burn off the carbonaceous material and separating solids and gases at the top of the reaction column;
introducing the separated particles into the upper part of the second fluidized bed reaction tower, while introducing an oxygen-containing gas into the lower part of the second reaction tower,
The reaction column is operated under fluidized bed conditions at a temperature suitable to burn off the carbonaceous material, the treated particles are removed from the bottom of the reaction column, and a portion of the treated particles is transferred to the bottom of the riser type reaction column. A method for removing carbonaceous materials from particles containing carbonaceous materials, the method comprising recycling such materials to a carbonaceous material. [Claim 2] Particles containing a carbonaceous substance are introduced into the lower part of the first riser type reaction tower, and at the same time, an amount of oxygen-containing gas smaller than the stoichiometric amount is introduced into the lower part, and a comparison is made at the lower part. carbonaceous material at such a rate that the flue gas at the top of the reaction column does not contain substantial amounts of oxygen under entrainment conditions with a relatively high density phase at the top and a relatively low density phase at the top. The reaction column is operated at a temperature suitable for burnout, solids and gas are separated at the top of the reaction column, and the separated particles are introduced into the top of a second fluidized bed reaction column, while the second reaction column introducing an oxygen-containing gas in the lower part of the reactor, operating the reaction column under fluidized bed conditions at a temperature suitable to burn off the carbonaceous material, and the flue gas in the upper part of the reaction column being substantially oxygen-free. carbonaceous material, consisting of establishing the amount of oxygen-containing gas in such a way, removing the treated particles from the bottom of the reaction column, and recycling a portion of the treated particles to the bottom of the riser-type reaction column. 2. The method of claim 1, wherein said material is removed from particles containing said material. 3. The method of claim 1, wherein the carbonaceous material-containing particles are FCC waste catalyst particles. 4. The temperature of the riser type reaction tower is 525°C to 725°C, and the temperature of the fluidized bed reaction tower is 62°C.
The method of claim 1, wherein the temperature is 5°C to 950°C. 5. A less than stoichiometric amount of oxygen introduced into the first reaction column is sufficient to burn off 20 to 70% of the carbonaceous material. Two ways. 6. The method according to claim 1, wherein a multistage fluidized bed reaction column is used as the second reaction column. 7. The density ratio of the relatively high density phase to the relatively low density phase is from 5 to 50, preferably from 10 to 30.
, more preferably about 20. 8. The ratio between the amount of particles removed from the second reaction column and the amount of particles recycled to the first reaction column is 0.
8. The method according to any one of claims 1 to 7, wherein the number is 1 to 10. 9. A first riser-type reaction column consisting of an elongated, usually vertical, reaction column with solid inlet means and gas inlet means in the lower part of the reaction column, connected to the top of the first reaction column. means for separating solids and gas, having a gas inlet and a solids outlet, connected to the solids outlet of the gas/solids separation means, and having a gas inlet means in the lower part of the reaction column; a second fluidized-bed reactor, usually a vertical reactor, provided with solids exit means and recirculating the solids from the second reactor to the first reactor; 1. An apparatus for removing carbonaceous materials from particles containing carbonaceous materials, the first reaction column and the second reaction column being connected by means for removing such materials. 10. The apparatus of claim 9, wherein the lower part of the riser reactor column has a larger diameter than the upper part of the reactor column. 11. The apparatus of claim 10, wherein additional gas inlet means are present above the lower part of the reaction column. 12. Apparatus according to claim 9, wherein the solids outlet means of the gas/solids separation means is connected to the upper part of the second reaction column. 13. Apparatus according to any one of claims 9 to 12, wherein the solids outlet means of the second reaction column is located in the lower part of that reaction column. 14. The apparatus according to claim 9, wherein the second reaction column is provided with an internal that makes it possible to create a multistage fluidized bed. 15. Apparatus according to claim 9, wherein the solids recirculation means is provided with a valve making it possible to adjust the recirculation ratio.