FI75590C - Circulating fabric bed pyrolysis process and reactor for circulating fabric bed pyrolysis. - Google Patents

Description

75590 1 Circulating fluidized bed pyrolysis process and reactor for circulating fluidized bed pyrolysis Circulationssvävbäddspyrolysprocess och Reaktor förulationssvävbäddspyrolys 5

The invention relates to a circulating fluidized bed pyrolysis process for pyrolysing organic materials, especially heavy hydrocarbons, to lighter hydrocarbons by contacting the pyrolyzable material in a pyrolysis step with an inert heat carrier material which is reheated

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The invention also relates to a reactor for fluidized bed pyrolysis to pyrolyze organic materials, especially heavy hydrocarbons, to lighter ones. hydrocarbons by contacting the pyrolyzable material in the pyrolysis step with an inert heat carrier material heated in the combustion step and where, after the pyrolysis reaction, the pyrolysis products are separated from the heat carrier material which is passed to the combustion step for reheating.

The pyrolysis of organic substances by means of a circulating finely divided heat carrier-25 material is known in the art. The pyrolysis process typically includes a pyrolysis reactor in which the material to be pyrolyzed is contacted with a hot inert heat carrier material, equipment for separating pyrolysis products from the heat carrier material, and a reactor in which at least a portion of the solid pyrolysis products are combusted to heat the heat carrier material.

The pyrolysis reaction can be carried out in various ways. Reactors are known in which the material to be pyrolyzed flows from the bottom upwards or from the top downwards. Horizontal reactors have also been used. The heat transfer material may be in a fluidized state in the pyrolysis reactor.

The invention relates generally to the latter technique, in which pyrolysis is carried out in a suspended finely divided heat transfer material. When pyrolysis is performed in a conventional reactor, the problem is often the control of the residence time. For example, when pyrolysing heavy oils 5 into lighter hydrocarbons, the fastest producing light products, such as ethylene and propylene, tend to further crack, producing large amounts of methane and coke and reducing the yield of more valuable products. On the other hand, heavier fractions would require a longer residence time to obtain a pyrolysis reaction far enough. In the fluidized heat carrier-10 material, the flow of feedstocks is not uniform because disturbance flows occur and as a result unevenness in the pyrolysis. In conventional reactors, pyrolysis is therefore difficult to carry out optimally.

It is an object of the invention to provide a circulating fluidized bed pyrolysis process in which the above-mentioned disadvantage is reduced so that the yield of valuable light products is as high as possible and the number of side reactions which produce less valuable products is as small as possible.

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The circulating fluidized bed pyrolysis process according to the invention is mainly characterized in that, in the pyrolysis step, the material to be pyrolyzed and the heat transfer material are passed through a substantially horizontal, substantially converging reaction space and the feedstock is fed from one or more at several points, that at least a portion of the pyrolysis products are removed from the center of the reaction space at an outlet near the centerline, and that the inert heat transfer material is removed from the reaction vessel.

The reactor according to the invention for circulating fluidized bed pyrolysis is mainly characterized in that the reactor has a substantially horizontal reaction space with a converging cross-section, that there are one or more feed points along the longitudinal axis of the reactor for feeding

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75590 l to fluidize the carrier material, that there is an outlet in the central region of the reaction space near the centerline to remove at least a portion of the pyrolysis product from the reaction space, and that there is a feed point at the beginning of the reactor

In the process of the invention, a finely divided heat carrier material heated to one end of a substantially horizontal reactor is passed together with a fluidizing gas that is substantially oxygen-free. The cross-sectional area of the reactor tapers in the flow direction. The convergence of the reactor cross-sectional area is generally relatively low and between 0.1 and 15 °, preferably between 2-5 °. The pyrolyzable material, for example heavy oil, is sprayed into the fluidized-bed carrier material at one or more points. By selecting the spray site, the residence time can be influenced to some extent. The inert hot heat carrier material releases heat and causes the pyrolytic decomposition of the organic material into lighter gaseous and liquid as well as solid carbonaceous products. As the pyrolysis proceeds, the heat transfer material cools and the heat transfer thus deteriorates. On the other hand, the reactor used in the process according to the invention decreases in cross-sectional area in the flow direction, as a result of which the flow rates of the products increase. The increase in velocity causes turbulence and more efficient heat exchange, which compensates for the cooling.

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In the pyrolysis process according to the invention, some of the product gases generated are removed from the central region of the reaction space in the vicinity of the center line. Much of the light products produced first are thus recovered before their secondary cracking and coking. The heavier, still pyro-30 unlysed fractions tend to follow the heat transfer material passing along the reactor walls. This gives more residence time for heavier fractions. The heat transfer material cooled at the end of the reactor and the remainder of the pyrolysis products are passed to a separator where they are separated from each other.

The product gases removed from the central area and the heat-bearing material they may contain can be led to the same separator or, if desired, to a separate separator. The separator is suitably, for example, a conventional cyclone separator, from the top of which gaseous and vaporized pyrolysis products are removed. They are passed through cooling to fractionation. From the bottom of the cyclone, the cooled heat carrier material 5 is separated from the products 5 and returned to the heating zone, where it is reheated to the temperature required for pyrolysis. During combustion, carbon waste adhering to the surface of the heat-bearing material particles burns and releases at least part of the required heat.

The solution according to the invention achieves significant advantages. The residence time in the reactor can be adjusted by selecting the oil / quench feed points. The converging reactor provides that the flow rate increases and can be pre-adjusted to suit the cyclone inlet. Due to the increase in speed, the need to add fluidizing gas also decreases at the end. In addition, the solids density increases, the heat transfer from the solids improves, and the reactions are better completed. The control of the residence time gives a "square efficiency", i.e. a small change has a very large effect.

The pyrolysis temperature varies depending on the quality of the starting material and the desired end products. In general, temperatures range from 500 to 1000 ° C, most preferably from 600 to 800 ° C. The heat carrier material which dissipates the heat required for pyrolysis is usually at a temperature higher than 100-300 ° C.

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In the circulating fluidized bed pyrolysis process according to the invention, various heat transfer materials can be applied which are generally known in the art:. The heat transfer material may also contain catalytic particles or materials chemically reactive with the feedstocks, such as desulfurizers, but is not a necessity. Preferably, the heat transfer material used in the reactor is relatively fine with a particle size ranging from 50 to 1000 microns. The recommended material is quartz sand, but some durable minerals such as feldspar and bauxite as well as coke are also suitable.

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In the fluidized bed pyrolysis process of the invention, a wide variety of materials can be pyrolyzed. Particularly suitable are heavy oil

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75590 1 products. Such are e.g. heavy base oils from the oil refining industry, bottom sludges from oil tanks, crude oil, waste oils, ion exchange resins, etc. The fluidized bed pyrolysis process according to the invention is also suitable for In general, any hydrocarbonaceous material is suitable for pyrolysis in the reactor of the invention.

The invention will be explained in more detail with reference to a preferred embodiment of the invention shown in the figures of the accompanying drawings, to which, however, the invention is not intended to be exclusively limited.

Figure 1 shows a circulating fluidized bed pyrolysis process 15 according to the invention in a schematic side view.

Figure 2 shows a sectional side view of the pyrolysis reactor used in the process of Figure 1.

Fig. 3 shows a section along the line II1-III in Fig. 2.

In Figure 1, the pyrolysis reactor used in the process of the invention is generally designated 10. In the circulating jet pyrolysis process of Figure 1, the inert heat-25 support material heated in combustion II circulates between pyrolysis stage A and combustion stage B. From the combustion chamber 11, one 12 leads to the separator 13. The flue gases and the combustion gases are discharged down to the IA. Reactor 10 has a feed device 15 in combustion step B for feeding heated inert hot heat carrier material to reactor 10. Reference numeral 16 denotes the supply of fluidizing gas. The feeders 17 spray the material to be pyrolyzed into the flowing hot heat transfer material from the circumference towards the center. Other fluidization gas supply points are indicated by reference numerals 18 and 19.

After the reactor 10 there is a separator 20. The products are discharged down to compound 21 35 and the heat carrier material is led down to compound 23 and 25 back to combustion stage B. Reference numeral 22 denotes a coolant supply to line 21. If desired, part of the heat carrier material 6 75590 1 can be removed up to 24 heat carrier and material density control. The combustion air is led to the combustion chamber 11 together via 26 and through the grate 27. The combustion chamber 11 is led by a connection 28, along which the supply of additional fuel and the additional supply of heat transfer material 5 to adjust the density can take place.

According to Figures 2 and 3, the material to be pyrolyzed is fed from several points 17 along the longitudinal axis of the reactor 10. The fluidizing gas is introduced into the reactor 10 from one or more points 16, 18 and 19. The zone A of the pyrolysis belt 10 is formed by a generally horizontal reaction space 10 with a cross-sectional area converging in the direction of flow, into which a hot heat carrier material is introduced. At least a portion of the pyrolysis products are removed from the outlet C near the centerline of the reaction space 10. The inert heat transfer material is brought into tangential circulation in the reaction space 10 by a fluidizing gas by feeding the fluidizing gas from the feed points 18. The funnel-shaped shape of the tube 29 is not necessary, but the tube 29 may just as well be completely straight. In the vicinity of the pyrolysis product outlet C, an additional fluidizing gas is introduced tangentially from the feed points 19 to force an inert heat transfer material onto the walls of the reaction space 10 in the vicinity of the funnel-shaped tube 29. Tangentially inert gas can be introduced to the walls of the reaction space 10 from the feed points 19 to provide an erosion-reducing gas mattress 25. In the vicinity of the wall of the reaction space 10, the feed points 19 are preferably arranged radially in the reactor 10.

The product gases generated in the pyrolysis process according to the invention are removed from the center of the reaction space 10. Much of the light products produced first are thus recovered before their secondary cracking and coking. The funnel-shaped tube 29 prevents secondary cracking. The heaviest, as yet non-pyrolyzed fractions tend to follow the heat transfer material passing along the walls of the reactor 10 of the earth.

This gives the heaviest fractions more residence time. The inert heat carrier material is separated from the pyrolysis products, after which it is carried out

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7 75590 1 cooling of pyrolysis products by passing cooling medium down the pipe 22 to the joint 21.

Only one preferred embodiment of the invention has been described above, and it will be clear to a person skilled in the art that numerous modifications can be made to it within the scope of the inventive idea set out in the appended claims.

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Claims (10)

A fluidized bed pyrolysis process for pyrolysing organic materials, especially heavy hydrocarbons, to lighter hydrocarbons by contacting the pyrolyzable material in the pyrolysis step (A) with an inert heat transfer material B), characterized in that in the pyrolysis step (A), the pyrolyzable material and the heat carrier material are passed through a substantially horizontal cross-sectional reaction space (10) so that the pyrolyzable material is fed from one or more points (17) along the reactor (10) longitudinal axis that the fluidizing gas for fluidizing the heat transfer material is introduced into the reaction space (10) at one or more points (16, 18, 19), that at least some of the pyrolysis products are removed from the central region of the reaction space (10) near the center line from the core discharge point (C), and that the inert heat transfer material is removed from the reaction space (10). 1 Claims Process according to Claim 1, characterized in that the inert heat-carrier material is brought into tangential rotation in the reaction space (10) by means of a fluidizing gas (18). Process according to Claim 1 or 2, characterized in that the pyrolysis products are removed via a pipe (29) in the vicinity of the center line of the reaction space. Process according to Claim 3, characterized in that an additional fluidizing gas (19) is introduced tangentially into the reaction space 50 (10) in the vicinity of the pyrolysis product outlet (C) in order to force the inert heat transfer material onto the walls of the reaction space (10) in the vicinity of the pipe (29). Process according to one of the preceding claims, characterized in that an inert gas (19) is introduced tangentially to the walls of the reaction space (10) to provide an erosion-reducing gas bed in the vicinity of the wall of the reaction space (10). II 9 75590 Ί 6. A reactor for circulating fluidized bed pyrolysis for pyrolysing organic materials, especially heavy hydrocarbons, to light hydrocarbons by contacting the pyrolyzable material in the pyrolysis step (A) with a inert heat transfer material (B), characterized in that the reactor (10) is a substantially horizontal reaction space with a converging cross-sectional area, that along the longitudinal axis of the reactor (10) there are one or more feed points (17) for feeding pyrolyzable material to the reaction space, that the reactor (10) has one one or more feed points (16, 18, 19) for introducing a fluidizing gas into the reaction space (10) to fluidize the heat transfer material so that there is an outlet (C) in the central region of the reaction space (10) near the center line to remove at least some of the pyrolysis products 15 from the reaction space (10), and that there is a feed point (15) at the beginning of the reactor for introducing the inert heat carrier material into the reaction space (10) and a discharge point at the end of the reactor (10) for removing the inert heat carrier material from the reaction space (10). 20 Reactor according to Claim 6, characterized in that the second fluidizing gas supply points (18) are arranged to lead the fluidizing gas into the reaction space (10) in order to cause the heat-transfer material in the reaction space (10) to rotate tangentially. Reactor according to Claim 6 or 7, characterized in that a funnel-shaped tube (29) is arranged inside the reactor (10) substantially in the vicinity of the center line of the reaction space in order to remove pyrolysis products from the reaction space (10). is 8 1 75590 Reactor according to one of Claims 6 to 8, characterized in that the third fluidizing gas supply points (19) are arranged to introduce additional fluidizing gas into the reaction space (10) to force an inert heat-transfer material on the walls of the reaction space (10) in the vicinity of the pyrolysis product outlet (C). 35 Reactor according to Claim 9, characterized in that the third fluidizing gas supply points (19) are arranged radially in the reactor (10). 10