DE4103450A1 - Pilot plant for small scale simulation of hydrocarbon cracking plant - enables direct transfer of performance results to full scale - Google Patents

Abstract

Prodn. of a uniform pulse-free cloud of flying powder (catalyst) in a small scale test installation with a riser reactor is claimed, primarily used for the catalytic cracking of hydrocarbons at a catalyst inlet temp. of 450-570 deg. C, an absolute pressure of 0.1-0.4 MPa and a throughput of 0.5-2 kg/hr of petroleum and 3-20 kg/hr of catalyst. The installation has a catalyst dosing arrangement in the form of a screw, pump, preheater, a riser reactor, a sepn. system for the catalyst and reaction prods., a regenerator (the fluidised bed reactor) for the catalyst and a condensing system for sepg. the liq. reaction prods.. USE/ADVANTAGE - The method makes use of a small scale or pilot plant that simulates the process conditions of full scale hydrocarbon fluid catalytic cracking (FCC) plants so that direct transfer of the results to full scale is ensured

Description

The invention relates to a method for generating an equal moderate cloud of dust in a small-scale test facility with a riser reactor for studies on the catalytic Cracking of hydrocarbons.

The catalytic cracking process, especially in the form of the fluid cata Lytic Cracking (FCC) takes on the conversion of high-boiling Hydrocarbon fractions and petroleum distillation residues High octane gasoline and olefins play a key role. In large-scale plants for catalytic cracking on a world scale as a reactor principle the riser reactor in various NEN variants enforced. The riser reactor consists of an ascending pipe that runs from the Reactor inlet (base point) to the reactor outlet from the catalyst / on blended product mixtures in a uniform cloud of dust is flowed through elevated temperatures, so that the cracking reaction can run.  

For the transfer of research results from laboratory reactors on the industrial scale, small-scale ver search systems or pilot systems in which the process conditions large-scale plants can be largely simulated, much tried and tested. However, an important prerequisite for this is that the same reactor principle as in the large-scale plant is realized. If different reactor principles apply is a direct transfer of results into the industrial scale not possible because only trend statements will hold. This is particularly true of the yield structure and the product qualities too. The application of the riser principle on a small scale relatively low catalyst throughputs is pronounced difficult because of a continuous catalyst flow in the form an even cloud of airborne dust as a function of time is absolutely necessary for an even reaction. A riser test facility is described in US Pat. No. 3,976,433. The riser reactor of this plant consists of a tube, the Diameter from 6.2 to 20.9 mm and its length from 0.3 to 6 m can be varied. This reactor tube is in loops attaches and is powered by an electrical resistance heater heated. The preheated, liquid insert pro product mixed with the catalyst heated to approx. 700 ° C and evaporates, forming a cloud of dust, which below Flow of the cracking reaction flows through the reactor. In the aftershell tied stripper, the reaction products from the catalyst separates. The catalyst is pneumatically in the regenerator promotes where it regenerates and then back into the reactor is returned.  

The catalyst throughput in this plant is regulated by a device which differs fundamentally from the catalyst metering of large technical plants. This Vorrich device ( Fig. 1) consists of a vertical tube ( 1 ) which runs in a wide arc ( 2 ) to the entrance of the riser reactor ( 4 ). In this vertical pipe section ( 1 ) a vertically displaceable pipe ( 3 ) is attached through which so much nitrogen is introduced that a fluidized catalyst bed is formed. This fluidized bed has a hydrostatic pressure as a function of its height, which acts from the tightly packed catalyst layer in the pipe bend ( 2 ) and leads to the metering of the catalyst into the riser reactor. By moving the vertical pipe ( 3 ) in the pipe section ( 4 ), the height of the fluidized bed, associated with the hydrostatic pressure and the metered amount of catalyst, can be changed.

The sum of the static and hydrostatic pressure must be greater than the sum of the pressure required to overcome the frictional resistance of the tightly packed catalyst filling in the pipe bend ( 2 ) and the pressure at the entrance of the riser reactor to ensure the catalyst flow according to the desired throughput.

When the liquid feed product is evaporated by the hot catalyst (approx. 700 ° C) occur at the entrance of the riserreak tors pressure fluctuations of about 2 kPa, which a uniform Catalyst flow and a smooth course of the cracking reaction no longer guarantee. For this reason, those are achieved Test results also not directly with those of large-scale Plants comparable.  

Another small-scale riser test facility is being developed by J. Co rella and co-workers (Ingenieria Quimica, May 1985, Pages 43-52).

The riser reactor is 2.5 m long and has an inner diameter from 10 mm. Critical points of this system are also Catalyst metering and the regulation of the catalyst throughput With continuous plant operation, i.e. H. at the circuit management tion of the catalyst through the plant, the regulation of the Catalyst throughput through a valve, which in the connection tube is attached between the regenerator and riser reactor. On Difficulties with such a scheme were already in U.S. Patent 3,978,433. Due to the low throughput of catalyst in one Small-scale pilot plant is not possible with the help a constant mass flow of catalyst to a valve put. The brief changes in catalyst throughput do not guarantee an even reaction and falsify the result of the reaction. In discontinuous Chen operation of the pilot plant is the catalyst a dosing screw in the regenerator, which at the same time as Serves as a catalyst preheater. The catalyst is applied in a fluidized bed in the regenerator heats. The same amount of catalyst as that of the fluidized bed fed by means of a dosing screw flows through an overflow pipe from the regenerator into the riser reactor. This one too Control method proves to be a disadvantage that in a real trained fluidized bed due to oil bubble formation the catalytic converter the amount of gate flowing through the overflow pipe, fluctuations and is thrown. These fluctuations do not guarantee the end formation of a uniform cloud of dust in the riser reactor and consequently adversely affect the course of the reaction and falsifying the test results.

The invention has for its object a method for Generation of a uniform cloud of dust, consisting of kata analyzer, hydrocarbons and a production auxiliary gas, in one small-scale riser reactor for the catalytic cracking of To provide hydrocarbons to the process conditions simulations of large-scale plants so that a direct Transferability of the results achieved in large-scale Scale is guaranteed.

The entire system is shown in Fig. 2. It is for process temperatures up to max. 800 ° C, normal pressure, catalyst throughputs from 4 to 20 kg / h and feed product throughputs from 0.5 to 2 kg / h. It consists of a riser reactor ( 8 ), a separation system for the separation of catalyst and reaction products ( 9 ), two intermediate catalyst tanks ( 10 , 11 ), the regenerator ( 5 ), preheaters for the feed product ( 12 ) and nitrogen ( 15 ), the feed dosing pump ( 16 ), the Katatordosiervorrich device ( 6 ) and a plant part for the BMSR technology ( 17 ). The most important component of the small-scale test facility is the riser reactor ( 8 ), which has the shape of an ascending tube and a length of 12.5 m and an inner diameter of 10 mm. The entrance of the riser reactor ( 8 ) is designed as a mixing point ( 7 ) for the catalyst, the auxiliary conveying gas and the feed product in such a way that pulsation-free evaporation of the feed product is ensured ( FIG. 3). The riser reactor ( 8 ) is followed by a separation system ( 9 ), in which the catalyst discharged from the riser reactor ( 8 ) is separated from the vaporous reaction product by a combination of impingement separator and cyclone as well as stripper and cyclone.

The two intermediate containers ( 10 , 11 ) have an inner diameter of 300 mm and a length of 650 mm. They are used to measure the amount of catalyst conveyed through the system by means of a load cell and to equalize the pressure between the reactor ( 8 ) and the regenerator ( 5 ) during batch transport of the catalyst into the regenerator ( 5 ). The regenerator ( 5 ) is designed as a fluidized bed reactor. Its size is determined by the amount of coke deposited on the catalyst, the amount of regeneration gas necessary to burn the coke, the rate at which the coke burns, and the amount of catalyst passed through. The regenerator ( 5 ) has an inner diameter of 300 mm and a length of 500 mm, plus a calming zone with a 400 mm inner diameter and a length of 140 mm. The inflow floor of the regenerator consists of a perforated plate with holes of approximately 100 µm in diameter. The regenerator ( 5 ) and the intermediate containers ( 10 , 11 ) are separated by a ball valve. The preheaters for the feed product ( 12 ) and the auxiliary gas ( 15 ) are pipe spirals 5 and 3 m long and 2 mm inner diameter. The preheater for the regeneration gas is also in the form of a tube spiral 7 m long and 6 mm inside diameter. The catalyst metering screw ( 6 ), the speed of which is infinitely variable, was designed for a throughput of 4 to 20 kg / h. All parts of the apparatus are made of stainless steel.

The riser reactor ( 8 ) is directly electrically heated by the tube wall representing the resistance. The separation system ( 9 ), the intermediate container ( 10 , 11 ), the regenerator ( 5 ), the preheater for the feed product ( 12 ), the auxiliary conveying gas ( 15 ), the regeneration gas ( 18 ) and the catalyst metering device ( 6 ) indirect electrical resistance heating heated.

The small-scale pilot plant can be operated continuously Lichem as well as with semi-continuous or discontinuous Catalyst circulation are operated. During trial operation is compliance with the specified parameters and consequently also a smooth course of the cleavage reaction combined with a very good reproducibility of the test results, guaranteed accomplishes.

The method of operation of the method according to the invention is described below:
During an experiment, the regenerated catalyst in the regenerator ( 5 ) and heated to 600 to 750 ° C. is transported through the metering screw ( 6 ) to the entrance of the riser reactor ( 8 ). In the mixing point ( 7 ), the hot catalyst is first whirled up with auxiliary conveying gas, which is preheated to 550 ° C, and brought into contact with the feed product, which is preheated to approx. 320 ° C and metered into the riser reactor ( 8 ) via a side nozzle . The preheated Einsatzpro product is evaporated by the hot catalyst with the formation of a uniform cloud of dust. This catalyst / a feed product mixture flows through the riser reactor ( 8 ) under the cracking reaction. By heating the riser wall and the amount of heat introduced via the catalyst, a temperature profile is formed from the first temperature measuring point approx. 1 m after the mixing point from 450 to 570 ° C. to the reactor outlet from 450 to 550 ° C. In the downstream separation system ( 9 ), the vaporous reaction product is first separated from the catalyst in a baffle separator with cyclone at temperatures of 450 to 550 ° C and then fed to the condensation part ( 14 ) of the plant for the separation of liquid reaction product and reaction gas.

The separated catalyst then passes through a stripper with cyclone, the reaction product which still adheres to the catalyst being separated off. In the first intermediate container ( 10 ) below, the amount of catalyst passed through is determined by a load cell at temperatures of 450 to 550 ° C. The second intermediate container ( 11 ), which has the same temperature as the first, serves as a buffer vessel and to compensate for the differential pressure from the riser reactor ( 8 ) to the regenerator ( 5 ). The regeneration of the catalyst takes place in the regenerator ( 5 ) in a fluidized bed at temperatures from 600 to 750 ° C with an air-nitrogen mixture as the regeneration gas. The residual coke content of the regenerated catalyst is approximately 0.01 parts by mass in%, based on the total mass of the catalyst. The regenerated catalyst is then returned to the riser reactor ( 8 ).

An essential feature of the invention is the design and function of the catalyst metering ( 6 ) and the mixing point ( 7 ) of the catalyst, auxiliary conveying gas (nitrogen) and feed product in combination with the regulation of the differential pressure between the regenerator ( 5 ) and the reactor ( 8 ). At the entrance to the riser reactor ( 8 ), pressure fluctuations occur which are caused by the pulsating evaporation of the liquid-metered product used on the hot catalyst in the mixing point ( 7 ).

In order to achieve a uniform catalyst circulation in the form of a uniform flue dust cloud, the differential pressure across the Katalysatordosierschnecke (6) must be less than the frictional resistance of the catalyst in the metering screw (6), so that the dosage of the catalyst only by the mechanical rotational movement of the dosing ( 6 ) can be done. According to the invention, this is achieved in that the pressure fluctuations are kept low by the geometrical arrangement and the dimension of the combination of catalyst, auxiliary conveying gas and feed product. This mixing point ( 7 ) is characterized in that the catalyst metered through the downpipe ( 7.1 ) into the reactor inlet ( 7.3 ) is whirled up by the conveying auxiliary gas introduced via the nozzle ( 7.2 ). The liquid feed product is metered into this homogenized flight dust cloud through the pipe socket ( 7.4 ), which is dispersed by preheated auxiliary gas before entering the reactor (7.5). This significantly increases the continuity of the metering of the feed product and achieves pulsation-free evaporation of the feed product on the hot catalyst. In addition, the differential pressure across the metering screw ( 6 ) is regulated within a range of ± 0.5 kPa by throttling the exhaust gas flow from the regenerator ( 5 ) by means of a process computer using an adapted computer program. Through this Differentialdruckre regulation a uniform cloud of airborne dust in the reactor ( 8 ) is sufficient, and temperature fluctuations immediately behind the mixing point ( 7 ) are largely eliminated. This constant reactor temperature leads to a uniform course of the reaction and to a very good reproducibility of the test results. The test results achieved can be directly transferred to the industrial scale.

The small-scale FCC pilot plant with riser reactor is characterized by the following examples.

example 1

In a small-scale FCC test facility with a riser reactor, the one with a 2-point differential pressure control between the regenerator and reactor was equipped, one in Table 2 was characteri vacuum gas oil with a catalyst / oil ratio of 9.2 and a temperature at the reactor outlet, which is not due to a steady flow of catalyst through the reactor between 515 and fluctuated at 535 ° C on a commercial FCC catalyst Split base of a USY zeolite. The results of this versu ches are summarized in Table 2 under No. 4. Among the applied process conditions was a conversion of the insert product of 64.2% by mass achieved. The yield at Cracked gasoline (boiling point -216 ° C) was 46.2% by mass, based on use, and the coke deposition on the catalyst was 4.6% by mass, based on use. The conversion of the feed product and the crack gasoline yields are significantly lower than when splitting the same Product with comparable process parameter setting in a large-scale FCC system (see experiment no. 10, table le 2).

A transfer of results from small to large technical scale is only by applying appropriate facto possible. A direct comparison of these results with those a small-scale FCC pilot plant with a riser reactor, such as described in US Patent 3,976,433, is not possible because at a slightly higher boiling feed product used and lower gap temperatures were applied.  

Example 2

In a small-scale FCC test facility with riser reactor, which was equipped with a mixing point according to the invention according to FIG. 3 and a 2-point differential pressure control between the riser reactor and regenerator, a vacuum gas oil characterized in Table 2 was used with a catalyst / oil ratio of 9. 2 and a temperature at the reactor outlet, which fluctuated between 519 and 531 ° C. as a result of a non-uniform catalyst flow through the reactor, on a commercial FCC catalyst based on a USY zeolite. The results of this test are summarized in Table 2 under No. 5. A conversion of 69.3% by mass was achieved under the process conditions used. The yield of cracked gasoline (boiling point -216 ° C.) was 47.5 parts by mass in%, based on the feed, and the coke deposition on the catalyst was 5.2 parts by mass in%, based on the feed. Compared to example 1 without a mixing point according to the invention, the conversion and the crack gasoline yield could be slightly improved, but they are still significantly lower than when the same feed product is split with comparable process parameters in an industrial plant (see experiment no. 11, table 2). As in Example 1, the results can only be transferred from small-scale to large-scale by using transfer factors.

Example 3

In the small-scale FCC Ver equipped according to the invention search system with riser reactor with a continuous Regulation of the differential pressure between the reactor and regenerator equipped, was a vacuum characterized in Table 2  gas oil with a catalyst / oil ratio of 9.4 and a tem temperature at the reactor outlet from 520 to 521 ° C, which over the total test period remained almost constant, on a commercial FCC catalyst cleaved on the basis of a USY zeolite. The he Results of this experiment are summarized in Table 2, No. 6 poses.

There was a conversion of the input product of 79.3 masses shares in% and a crack gasoline yield of 52.6 masses shares in%, based on stake, reached. The coke separation on the catalyst was 5.4% by mass, based on Commitment. These results were confirmed by several repetitions search (Table 2; Experiment No. 7-9) under the same conditions confirmed, and it became a very good simulation of large-scale Process conditions combined with a very good reproducibility of the test results. The test results from the small-scale FCC system are comparable to those from a large-scale FCC system (Ta belle 2, Experiment No. 10), and a transfer to large-scale African scale is possible without transfer factors. At a Comparison of the achieved in the FCC test facility according to the invention Results with results from Akzo, which are in a small Technical FCC test facility with riser reactor during the splitting a vacuum gas oil with slightly higher boiling points below comparable process conditions were obtained (Table 1, Experiment No. 3), you can see that in the invention equipped small-scale FCC pilot plant a better one Simulation of the process conditions of a large-scale FCC system is possible than in the test facility mentioned above. In addition to one higher conversion also became a higher crack gasoline yield reached.  

Table 1

Table 2

Claims (1)

Process for generating a uniform, pulsation-free cloud of flying dust in a small-scale test facility with a riser reactor, primarily used for the catalytic splitting of hydrocarbons at catalyst inlet temperatures of 450 to 570 ° C, a pressure of 0.1 to 0.4 MPa, absolute, and mass flow rates of 0.5 to 2 kg / h petroleum product and 3 to 20 kg / h catalyst and consisting of a catalyst metering device in the form of a metering screw ( 6 ), a feed product metering pump ( 16 ), a preheater for the feed product ( 12 ), a riser reactor ( 8 ) in the form of an ascending pipe, a separation system ( 9 ) for the separation of catalyst and reaction products in the form of a combination of impact separator with cyclone and stripper with cyclone, a regenerator ( 5 ) in the form of a fluidized bed reactor for regeneration of the catalyst, one Condensation system ( 13 , 14 ) for separating the liquid reaction products as well a system part for the BMSR- equipment (17), characterized in that the geometric Ge staltung the Zusammenrührung of catalyst, feedstock and feed auxiliary gas is made as a mixing point (7) in a confined space, wherein first of all by the metering screw (6) via the drop tube ( 7.1 ) catalyst dosed into the reactor inlet ( 7.3 ) through the conveying auxiliary gas introduced through the nozzle ( 7.2 ) and then the preheated feed product dispersed through auxiliary gas ( 7.5 ) is metered into this homogenized cloud of dust over the nozzle ( 7.4 ) and the differential pressure is above the catalyst metering screw ( 6 ) is regulated.