FIELD OF THE INVENTION The present invention relates to the field of chemical engineering. In particular, examples of the invention relate to a slurry-bed reactor for enhancing particle suspension, liquid-solid mixing, heat transfer and mass transfer through external materials circulation. The present invention further relates to methods of conducting the slurry-bed reaction using slurry-bed reactors.

BACKGROUND

With oil resources decreasing worldwide, development of alternative energy technology has been paid more and more attention. Products such as cleaner fuel and wax with high quality can be produced by producing synthesis gas from carbon and hydrogen-containing raw materials such as coal, natural gas, and biomass, processing the synthesis gas with water-gas shift and purification, and using the synthesis gas as the raw material to produce hydrocarbons through Fischer-Tropsch synthesis technology, and meanwhile producing the byproducts of oxygenated compounds, then adopting mature petroleum processing technology. The core of the technical path is Fischer-Tropsch synthetic technology.

There are two types of catalysts which are used in liquid fuel production by Fischer-Tropsch synthesis using coal or natural gas as raw materials. One type is iron-based catalysts and the other is cobalt-based catalysts. Iron-based catalysts need to be replaced every 70-100 days due to poor stability. The frequent replacement of the catalysts limited the development of this technology. With better stability, cobalt-based catalysts could avoid frequent replacement of the catalysts and can be used in Fischer-Tropsch synthesis in fixed-bed reactors. However, a Fischer-Tropsch synthesis reaction is an exothermal reaction. A Fischer-Tropsch synthesis in a fixed-bed reactor is prone to problems such as hotspot and coking, which makes it difficult for scale-up. Later, Fischer-Tropsch synthesis reactors have been developed as circulating fluidized beds, fixed fluidized beds, and slurry beds. However, in a circulating fluidized bed, the fluidization process can be hard to control; the utilization rate of catalysts may be low with serious attrition; and the production capacity is often still low. A fixed fluidized bed has simple structure and can overcome the problems of low catalyst utilization rate and serious attrition. However, it is applied only to high-temperature Fischer-Tropsch synthesis rather than the production of high value-added heavy fraction such as clean diesel and wax.

Comparing with conventional gas-solid fluidized beds, the bubbling slurry-bed reactor technology, which comprises the gas-liquid-solid tri-phases, possesses advantages in many aspects. First, the reaction heat can be effectively removed and the reaction temperature can still be effectively controlled using a highly active catalyst (i.e. a high yield catalyst) so that the reactor is relatively easy to scale up and realize single-series large-scale industrialized production. Second, the reactor is usually approximately operated isothermally and the high value-added liquid hydrocarbon products such as clean diesel and heavy wax can be produced as the main products by selecting suitable catalysts and reaction temperature. Third, the operation environment of catalysts can be improved and thus the attrition of catalysts can be decreased. The average life of catalysts is well under control by regular replacement of catalysts. Therefore, slurry-bed reactor technology has become a leading technology in producing diesel and wax as the main products by Fischer-Tropsch synthesis. In addition to the Fischer-Tropsch synthesis process, slurry-bed reactors also have wide application potential in other reaction processes involving the gas-liquid-solid tri-phases.

A slurry-bed reaction relates to mass transfer, heat transfer and reaction among gas-liquid-solid tri-phases. Key features for the whole reaction is the microcosmically well-distributed particle suspension and uniform liquid-solid mixing. Otherwise, a slurry-bed reactor will likely have the problem of reaction hotspot similar to a fixed-bed reactor due to agglomeration of particles, and therefore affect heat stability of the whole operation of the reactor. Being aware of this fact, the design of a slurry-bed reactor should preferably meet two basic requirements. First, in order to maintain the features of a slurry bed, the catalysts should preferably be prepared as fine particles with sufficient mechanical strength through particular forming process to ensure well-distributed suspension in liquid slurry materials. Second, the reactor diameter should preferably be selected to make sure that the raw material gas is able to get through the slurry bed layer with bubbling at a certain superficial gas velocity. It will cause a risk of sedimentation and agglomeration of catalyst particles if the raw material gas passes through the slurry bed layer at a gas velocity which is too slow. On the other hand, it could cause serious tail gas entrainment and particle entrainment if the gas velocity is too high.

However, comparing with the liquid medium, the density of gas medium is limited. The superficial gas velocity of a bubbling slurry bed is also limited to a limited range so that the kinetic energy provided by the bubble with a certain gas velocity is also limited for particle suspension and enhancement of mass transfer and heat transfer. For the design of a slurry-bed reactor for a Fischer-Tropsch synthesis, one of the key technologies is still how to design the enhanced turbulence and suitable internal components to enhance the particle suspension and uniform liquid-solid mixing, as well as mass transfer, heat transfer and reaction among the three phases in the whole reactor.

Therefore, persons skilled in the art still desire to develop a slurry-bed reactor with improved particle suspension and liquid-solid mixing effects.

DETAILED DESCRIPTION OF THE INVENTION In order to solve the above problems, the present invention provides a new design of the external circulation apparatus of a reactor, and further improves the positions of the injectors and the descending pipes. Preferably, the position, number and angles of the injectors which spray externally circulated materials into the reactor vessel match the descending pipes provided in the center of the slurry-bed reactor. In addition, the liquid from the outlet of the injectors has sufficient velocity head (engineering terminology, kinetic) in order to ensure sufficient thrust force and spiral tangential stirring force, thereby significantly improving the particle suspension and the mixing effect of liquid-solid in the slurry bed reactor.

In one aspect of the present invention, there is provided a slurry-bed reactor comprising: a reactor vessel, at least one center descending pipe in the reactor vessel, at least one center injectors in the center descending pipe, a plurality of peripheral injectors provided along an inner wall of the reactor vessel and a gas distributor at the bottom of the reactor vessel, a middle external circulation apparatus and/or a top external circulation apparatus, the middle external circulation apparatus draws out at least a portion of slurry materials and at least a portion of the slurry materials is recycled back to the reactor vessel, the top external circulation apparatus draws out at least a portion of gas materials in the reactor vessel and at least a portion of the gas materials is recycled back to the reactor vessel, wherein the peripheral injectors are provided along the inner wall of the reactor vessel. The opening of at least one of the peripheral injectors is directed obliquely upwardly and form an angle of 5°~ 80°, preferably 10°~60°with the horizontal plane,. The horizontal vector of the opening direction of the peripheral injectors (13) is tangential to an inner wall of the reactor vessel (1).

In one aspect of the present invention, the height difference between the gas distributor and the nearest peripheral injector to the gas distributor is at least 1%, preferably at least 2.5%, of the height of the reactor vessel, or is no more than 20%, preferably no more than 10%, of the height of the reactor vessel. In one aspect of the present invention, the height difference between the nearest peripheral injector to the gas distributor and the farthest peripheral injector to the gas distributor is at least 40%, preferably at least 50%, of the height of the reactor vessel, or is no more than 90%, preferably no more than 80%, of the height of the reactor vessel.

In one aspect of the present invention, there is at least one peripheral injector located between the nearest peripheral injector to the gas distributor and the farthest peripheral injector to the gas distributor and the peripheral injectors are evenly spaced between each other in the vertical direction. Each peripheral injector is provided in the same clockwise direction or counterclockwise direction. Preferably, in a top view of the reactor, the peripheral injectors are distributed evenly spaced along the inner wall of the reactor vessel.

In the second aspect of the present invention, there is provided a method for conducting a slurry bed reaction, using the slurry-bed reactor of the present invention, said method comprises the following steps: i) supplying gas reactants to the gas distributor, the gas ascends in the space in the reactor vessel and outside of the center descending pipes after getting through the gas distributor and drives the ascending of the slurry, and reacts in the presence of catalyst in the slurry; ii) the resulting gas materials carrying an amount of slurry ascend to the upper part of the reactor vessel, the gas materials are drawn out by the top external circulation apparatus, gas in the gas materials are separated from the carried slurry, then at least a portion of the separated liquid materials are recycled back into the reactor vessel, preferably through the center injectors and peripheral injectors; iii) optionally, at least a portion of the slurry materials is drawn from the reactor vessel by the middle external circulation apparatus, liquid materials in the slurry materials are separated from solid materials, and at least a portion of the separated liquid materials are recycled back into the reactor vessel, preferably through the center injectors and peripheral injectors; iv) a portion of the slurry materials flows into the center descending pipes from the top opening of the center descending pipes, flows downwardly in the center descending pipes, and flows out from the bottom opening of the center descending pipes, then ascends again in the space in the reactor vessel and outside of the center descending pipes driven by the gas reactants, and repeat the foregoing steps (i)-(iv); wherein, the liquid materials circulated back through the top external circulation apparatus and the middle external circulation apparatus are sprayed from the peripheral injectors (13) obliquely upwardly, forming an angle of 5°~ 80°, preferably 10°~60° with the horizontal plane; and the liquid materials are sprayed from the center injectors (15) downwardly.

In the third aspect of the present invention, there is provided a method for conducting a slurry bed reaction, using a slurry-bed reactor of the present invention, comprising a reactor vessel including a slurry material, the method comprising the following steps: i) supplying gas reactants to a gas distributor so that the gas reactants ascend in the reactor vessel to drive the ascending of the slurry material in the reactor vessel and allow the gas reactants to react in the slurry material; ii) drawing at least a portion of resulting gas materials out of the reactor vessel from an upper region of the reactor vessel, gas in the resulting gas materials are separated from the carried slurry materials, then at least a portion of the separated liquid materials are recycled back into the reactor vessel, preferably through the center injectors (15) and peripheral injectors (13); iii) optionally, a portion of the slurry materials is drawn from the reactor vessel, liquid materials in the slurry materials are separated from solid materials, and at least a portion of the separated liquid materials are fed back into the reactor vessel, preferably through the center injectors and peripheral injectors; iv) passing a portion of the slurry materials downwardly through the center descending pipes by going in from the upper openings of the center descending pipes, and out from the lower openings of the center descending pipes, the slurry materials ascending again in the reactor vessel and outside of the center descending pipes driven by the gas reactants, wherein, the slurry materials drawn in step ii) and step iii) are sprayed from the peripheral injectors obliquely upwardly, forming an angle of 5°~ 80°, preferably 10°~60° with the horizontal plane; and the liquid materials are sprayed from the center injectors downwardly.

In some embodiments of the present invention, before the resulting gas materials are drawn from the reactor vessel in the aforementioned method for conducting slurry reaction, the resulting gas materials are separated preliminarily in the reactor vessel, separating the gas materials from the slurry contained therein.

DETAILED DESCRIPTION OF DRAWINGS

Certain embodiments of the present invention are described in more detail in combination with the drawings.

Figure 1 is a schematic diagram of a slurry-bed reactor according to an embodiment of the present invention.

Figures 2 A and 2B are sectional views of an embodiment using two peripheral injectors.

Figures 3A and 3B are sectional views of an embodiment using three peripheral injectors.

Figures 4A and 4B are sectional views of an embodiment using four peripheral injectors.

Figure 5 is a schematic diagram of a slurry-bed reactor using multi-level center descending pipes according to another embodiment of the present invention.

Figure 6 is a sectional view of an embodiment of the reactor in Figure 5 using two peripheral injectors.

Figure 7 is a sectional view of an embodiment of the reactor in Figure 5 using three peripheral injectors. Figure 8 is a sectional view of an embodiment of the reactor in Figure 5 using four peripheral injectors.

Figure 9 is a schematic diagram of a Venturi injector used as a center injector.

Figures 10A and 10B are schematic diagrams of tubular injectors with a plurality of open pores on the top of a center injector.

Figure 11A is a schematic diagram of a preferred spraying manner of the center injector of the present invention.

Figure 1 1B is a schematic diagram of another preferred spraying manner of the center injector of the present invention.

Description of Reference Numbers in the Drawings

1. Reactor vessel;

2. Gas-liquid interface;

3. Gas-liquid separation

4. Condenser;

5. Gas-liquid separator;

6. Waste liquid;

7. Condensed liquid;

8. Tail gas;

9. Circulation gas;

10. Circulation pump;

1 1. Heater;

12. Ejecting liquid of center descending pipes;

13A. 13B. 13C. 13D. Peripheral injectors;

14. 14A. 14B. Center descending pipes;

15. 15A. 15B. Center injectors;

16. Liquid-solid separator in the reactor;

17. Slurry with low solid content;

18. Pressure relief valve;

19. Gas-liquid separator; 20. Tail gas;

21. Secondary liquid-solid separator;

22. Liquid product;

23. Circulation pump;

24. External circulation slurry with low solid content;

25. Gas compressor;

26. Gas reactant materials;

27. Gas distributor

101. Blocking component

102. Opening surface

103. Open pore

EXAMPLES The "range" disclosed herein is in the form of lower limit and upper limit.

There can be one or more lower limits, and one or more upper limits, respectively. A given range is preferably limited by selecting a lower limit and an upper limit. The selected lower limit and upper limit will determine the boundary of the specific range. The range limited by such way can be included or combined, i.e. any lower limit and any upper limit can be combined to form a range. For example, the range of "60-120 and 80-1 10" that is given by specific parameters can be understood to be 60-1 10 and 80-120. In addition, if a minimum value is 1 and 2, and a maximum value is 3, 4, and 5, the following range can thus be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. Unless otherwise specified, all of the embodiments and preferred embodiments described herein can be combined to obtain new examples.

Unless otherwise specified, all of the technical features and preferred features described herein can be combined to obtain new examples.

Unless otherwise specified, all of the steps described herein can be performed in order or in a different order, preferably in order. For example, a method comprises steps (a) and (b) may mean the method can comprise steps (a) and (b) in such order, or steps (b) and (a) in such order. For example, a method further comprising step (c) means step (c) can be added into the method in any order, for example, the method may comprise steps such as steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

Figure 1 shows an embodiment of the slurry-bed reactor of the present invention. It can be found from the figure that the reactor includes two portions, i.e. the portion in the reactor vessel and the portion outside of the reactor vessel. The inside of the reactor vessel 1 includes a center descending pipe 14, a center injector 15, a plurality of peripheral injectors (e.g. 13A, 13B) and a gas distributor 27 at the bottom of the reactor vessel 1. The reactor vessel 1 can contain slurry materials, which can be any slurry formed by dispersing solid materials into liquid materials. The reactor vessel 1 includes a middle external circulation apparatus that can draw at least a portion of the slurry materials from the reactor vessel and recycle at least a portion of the slurry materials externally and back to the reactor vessel 1. Under normal working conditions, the middle external circulation apparatus can be used for drawing and recycling externally the slurry materials from beneath a gas-liquid interface 2 from the reactor to the center injector 15 and peripheral injectors 13A, 13B. The slurry-bed reactor further includes a top external circulation apparatus that can be used for drawing at least a portion of the resulting gas materials from the reactor vessel 1. Under normal working conditions, the top external circulation apparatus can be used for separating the slurry materials from the resulting gas materials and drawing at least a portion of the gas materials from the reactor vessel and recycling externally at least a portion of the liquid materials separated from the gas materials back into the reactor vessel, preferably through the center injectors 15 and peripheral injectors 13 A, 13B. The resulting gas materials may include gas products obtained from the slurry-bed reaction and gas raw materials that have not reacted in the reaction. The gas raw materials may include gas reactants and inert gases that do not react. The gas reactant materials 26 which are needed in the reaction process are delivered to the gas distributor 27 by automatically or manually controlled components that are known in the art such as pipes, valves, controlling device and so on. It can further optionally comprise pumps, pressure devices, decompressors, heating devices, cooling devices, detection devices, etc. according to the requirements of the process. The gas reactant materials 26 can comprise any gas materials that are required for a reaction process, for example, reactants, inert diluent gas, gas used for inactivating the reaction system to stop the reaction, etc. These gas materials can be mixed first, and then delivered to the gas distributor 27, or can deliver multiple gas materials simultaneously to the gas distributor 27 according to the desired ratio by a plurality of parallel pipes.

The gas distributor 27 is located at the bottom of the reactor vessel 1 and can be any gas distribution device well-known in the art, for example, gas distribution plates containing a plurality of pores, gas distributors containing injector structures, etc.

In one embodiment of the present invention, above the gas distributor 27, two peripheral injectors 13A and 13B are provided along the inner wall of the reactor vessel 1, as shown in Figures 2A and 2B. Shown in the top view in Figure 2A, the two peripheral injectors 13A and 13B are provided along the tangential direction of the inner wall of reactor vessel 1 in a central symmetric way and along the same counter-clockwise direction, slurry materials from the middle and top external circulation apparatus are ejected from the injector along the direction (i.e. tangential direction) indicated by the arrow in Figure 2A. It can be found in Figure 2B that there is a certain acute angle between the peripheral injector and the horizontal plane, the acute angle is preferably 5°~ 80°, more preferably 10°~60°.

Preferably, the positions of these peripheral injectors are defined in the present invention. In particular, in one embodiment, the height difference between the gas distributor 27 and the nearest peripheral injector 13 to the gas distributor 27 (e.g. peripheral injector 13B in Figure 1, peripheral injector 13C in Figure 3 A, peripheral injector 13D in Figure 4B) is at least 1%, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, preferably at least 2.5%, of the height of the reactor vessel (the height of the reactor vessel is the distance between the top sealing head and the bottom sealing head which is marked as L in the Figure 2B), or is no more than 20%, such as 20%, 15%, 14%, 13%, 12%, 1 1%, 10%, 9% or 8%, preferably no more than 10%, of the height of the reactor vessel.

In an embodiment of the present invention, the height difference between the nearest peripheral injector to the gas distributor and the farthest peripheral injector to the gas distributor (e.g. peripheral injector 13A in Figure 1, Figure 2B and Figure 3B) is at least 40%, such as 40%, 45%, 50%, 55% or 60%, preferably at least 50%, of the height of the reactor vessel, or is no more than 90%, such as 90%, 85%, 80%, 75% or 70%, preferably no more than 80%, of the height of the reactor vessel.

In an embodiment of the present invention, the height from the gas distributor 27 to the gas-liquid interface 2 of the slurry materials in the reactor vessel under normal working conditions is defined as H (e.g. H in Figure 2B), thus the height difference between the gas distributor 27 and the nearest peripheral injector to the gas distributor is 2 ~20 H, preferably 5%~10%H, the remaining peripheral injectors are provided between the gas-liquid interface and the nearest peripheral injector to the gas distributor, preferably provided evenly spaced out in height.

In an embodiment of the present invention, the ejecting kinetic energy per unit volume of the liquid materials ejected from the peripheral injectors is 0.001-0.05 W/m ³ , preferably 0.002-0.04 W/m ³ , for example, at least 0.001 W/m ³ (e.g. 0.00 lW/m\ 0.002 W/m\ 0.003 W/m\ 0.004 W/m\ 0. 005 W/m ³ or 0.008 W/m ³ ), or for example no more than 0.05 W/m ³ (e.g. 0.01 W/m\ 0.02 W/m\ 0.03 W/m\ 0.04 W/m 3 or 0.05 W/m 3 ). In an embodiment of the present invention, the positions of the injectors in the reactor vessel can be adjusted.

More peripheral injectors can also be used in the present invention. For example, Figures 13 A, 13B and 13C show the situation of using three peripheral injectors 3A, 3B and 3C. In an embodiment of the present invention, there is at least one peripheral injector located between the nearest peripheral injector to the gas distributor and the farthest peripheral injector to the gas distributor (e.g. peripheral injector 13B in Figure 3B). Seen from top view in Figure 3A, these three peripheral injectors are evenly and tangentially distributed along the inner wall of reactor vessel 1. From Figure 3B, these three peripheral injectors are provided in layers, and the angles between them and the horizontal plane are also 5°~ 80°, more preferably 10°~60°. The height difference between the gas distributor and the nearest peripheral injector to the gas distributor is 2 % ~20 % H, preferably 5%~10%H. The remaining peripheral injectors are provided between the gas-liquid interface and the nearest peripheral injector to the gas distributor, preferably provided evenly spaced out in height or provided unevenly spaced out in height. Figures 4 A and 4B show the configuration having four peripheral injectors 13A-13D, which are also provided according to the above-mentioned manner. The present invention can further comprise more peripheral injectors, and the setting of their angles and positions are as described above. Although it is shown in the drawings as described herein that there is only one peripheral injector provided at each height, two or more peripheral injectors can be further provided at each height. For example, regarding the reaction equipments with large volumes, n layers can be provided, and each layer comprises m peripheral injectors, wherein, n>3, m>3. In an embodiment of the present invention, the reactor vessel comprises 2, 3, 4, 5 or 6 layers of peripheral injectors located along the inner wall of the reactor vessel, each layer comprises 2, 3 or 4 peripheral injectors located at the same vertical height. In an embodiment of the present invention, the peripheral injectors located in the same layer are evenly placed from each other in the horizontal direction.

In an embodiment of the present invention, the horizontal vector of the opening direction of a peripheral injector is tangential to an inner wall of the reactor vessel and is provided with the same clockwise or counterclockwise manner. In an embodiment of the present invention, in a top view of the reactor, the peripheral injectors are distributed evenly spaced along the inner wall of the reactor vessel.

A center descending pipe 14 is provided in the reactor vessel 1 along the axial direction. The center descending pipe 14 is longitudinally provided along the axis of reaction vessel 1. A blocking component 101 is provided at the bottom opening of center descending pipe 14. The cross-section area of the block component 101 along the horizontal direction and facing the gas distributor 27 is generally larger than the cross-section area at the bottom opening of the center descending pipe, and thus prevents the direct entrance of up flow from the gas distributor 27 into the center descending pipe 14, and therefore affects the homogeneity and flowing performance of the slurry therein.

One center descending pipe can be used in the present invention. However, the situation of using multi-level center descending pipes can also be considered. For example, Figure 5 shows an embodiment of using two center descending pipes. The reactor in Figure 5 is substantially the same as that in Figure 1. The difference only lies in the use of two center descending pipes 14A and 14B. It can be found from Figure 5 that these two center descending pipes are both provided along the axis with their head and tail aligned along the axial direction. Center injectors 15A and 15B are inserted into the inside of each center descending pipe. The same blocking components 101 are provided at the lower opening of each center descending pipe. According to specific reaction process and the size of a reaction system, the reactor can comprise 2-10 center descending pipes, preferably 2-4 center descending pipes. When comprising a plurality of center descending pipes, these center descending pipes are aligned as shown in Figure 5, and provided along the axis of the reactor with aligned head and tail. Figures 6-8 show the embodiments with two, three and four peripheral injectors in reactor vessel 1 of the reactor as shown in Figure 5, respectively. These peripheral injectors are provided in the same way as those shown in Figure 2A to Figure 4B. The unnecessary details will not be given again here.

Center injector 15 provided in the center descending pipe can be any injectors, Figure 9 shows a schematic diagram of a Venturi injector that can be used as center injector 15. The opening surface 102 of this Venturi injector is provided downwardly. The internal diameter of the pipe near the opening is gradually narrowed and then gradually enlarged. Such change of internal diameter of the pipe will ensure the corresponding increase in pressure and flow velocity of the liquid getting through the Venturi tube, and thus provide stronger driving force for the descending of slurry materials in the center descending pipe. Similarly, Figure 10A shows a tubular injector with a plurality of open pores on the top. The tubular injector can be used as center injector 15. The opening is pointed downward. The opening surface 102 is with a plurality of open pores 103 as shown in Figure 10B. The other parts are closed. A plurality of open pores 103 as shown in the figure are provided on the opening surface 102 in a manner of center symmetry. However, they can also be provided in other manners as needed. The ejecting direction of the liquid ejected from the plurality of open pores 103 can be vertical to the opening surface 102 or oblique. In a most preferable embodiment, the ejecting direction of the liquid ejected from the plurality of open pores 103 is distributed in a cone shape by taking one point on the central axis of the tubular injector and above the ejection surface as the vertex, and taking the ejection surface as the bottom side (see Figure 1 1 A). More preferably, the ejecting direction of the liquid is oblique with the same angle on the lateral side of the cone to ensure that the direction of liquid ejected from each open pore will not go through the vertex of said cone (see Figure 1 I B). Such special setting can also provide stronger driving force for the descending of slurry materials in the center descending pipe. The distance between the opening of center injector 15 and upper opening of center descending pipe 14 is 1 %~10% of the total length of the center descending pipe 14, preferably 2%~5%. In certain embodiments of the present invention, the distance is at least 2.5% or 3% of the total length of the center descending pipe 14. In certain embodiments of the present invention, the distance is no more than

9% or 10% of the total length of the center descending pipe 14. The peripheral injectors of the present invention can have the same structure as the center injectors. However, the spraying direction is upward or obliquely upward. They can also be suitable injectors with any other structures.

The reactor vessel 1 can be filled with slurry when it is in use. For example, for a Fischer-Tropsch reaction, the slurry can be formed by solid materials such as the corresponding catalysts suspending in the materials such as liquid solvents, products, by-products, etc. Gas-liquid interface 2 of the slurry is higher than the height of said center descending pipes, center injectors and peripheral injectors, so that the latter are all located beneath the gas-liquid interface 2.

The middle external circulation apparatus and top external circulation apparatus are also provided outside of the reactor vessel 1. The middle external circulation apparatus comprises liquid-solid separator 16, gas-liquid separator 19, circulation pump 23 and optional heater 1 1, or comprises liquid-solid separator 16 and circulation pump 23 only. It may optionally comprise gas-liquid separator 19 when the slurry materials that are recycled externally carry excess gas. The liquid-solid separator 16 is placed beneath the gas-liquid interface 2 for conducting solid-liquid separation and drawing a portion of slurry. The liquid-solid separator 16 can be one or more conventional filters. It can be also a liquid-solid cyclone separator. The filtered slurry 17 with low solid content is delivered to gas-liquid separator 19 by a pressure relief valve 18. The gas separated from liquid is directly discharged as tail gas 20 or delivered for post-processing process. Further solid-liquid separation or liquid-liquid separation is conducted in liquid-solid separator 21 for the liquid to remove any gas. The valuable liquid reaction product 22 is removed from the reaction system. Then the remaining liquid, i.e. the external circulation slurry 24 with low solid content passes through circulation pump 23 and is heated to reaction temperature in optional heater 1 1 , and then sent back to center injector 15 and peripheral injectors 13A and 13B, and thus complete the middle external circulation process of slurry. In this middle external circulation apparatus, the liquid-solid separator, gas-liquid separator, circulation pump and heater can be any suitable devices well-known in the art. However, in a preferable embodiment, the circulation pump is preferably a circulation pump with open blade impeller. Such circulation pump is with strong particle wearable performance. Meanwhile, it is helpful for slowing down the particle attrition of catalysts. The top external circulation apparatus comprises condenser 4, gas-liquid separator 5, circulation pump 10 and optional heater 1 1. Gaseous products or by-products are entrained with some liquid. Even the solid materials leave the gas-liquid interface 2 and ascend to gas-liquid separation zone 3, where a certain degree of gas-liquid or gas-solid separation is taken place, and then goes to the outside of reactor vessel 1 , and condensed in condenser 4. Sufficient gas-liquid separation occurs in gas-liquid separator 5. The worthless components in the gas phase isolate is discharged as tail gas 8 or delivered to the other post-processing process. The unreacted gas raw materials are used as circulation gas 9 and re-delivered to gas distributor 27 together with fresh gas reactant raw materials after being compressed by gas compressor 25. A portion of the separated liquid components (e.g. Ci ₂ -C ₃ o heavy hydrocarbons) is discharged as a certain liquid product 6. Recyclable liquid components (e.g. C ₅ -Ci ₀ light hydrocarbons) pass through circulation pump 10 as external circulation materials and are heated to desired reaction temperature in optional heater 1 1 , and then sent back to center injector 15 and peripheral injectors 13A and 13B, and injected into the reactor vessel. In the present invention, the middle external circulation apparatus and the top external circulation apparatus can use the same heater. Alternatively, the middle external circulation apparatus and the top external circulation apparatus can each include a heater. In certain embodiments of the present invention, the middle external circulation apparatus and the top external circulation apparatus each includes a heater, wherein the top external circulation apparatus may use the aforementioned heater, the middle external circulation apparatus includes an additional heater at a location after the externally circulated slurry 24 with low solid content passes circulation pump 23 and before it returns back to injector 13.

In particular, the external circulation liquid of the present invention can be oil phase generated by despumation, condensation, phase separation and dehydration of the gas phase products from the top of the reactor. It can be also slurry phase beneath the slurry surface. However, either one can provide external circulation materials for the injectors. For example, only the top external circulation apparatus is used to provide external circulation materials, or only the middle external circulation apparatus is used to provide external circulation materials. It is preferable to use top external circulation apparatus to provide external circulation materials. The external circulation materials can be provided by both the middle external circulation apparatus and the top external circulation apparatus.

By using a slurry-bed reactor as disclosed herein, the present invention may provide a slurry-bed reaction method with improved material circulation and stability. In particular, examples of the method can be conducted based on the following steps: first, gas reactant materials 26 such as synthesis gas are supplied to gas distributor 27 from the gaseous materials feeding element 26, the gas reactants are uniformly distributed or distributed according to a specific manner after getting through the gas distributor, the gas reactants ascend in the space in the reactor vessel 1 and outside of the center descending pipes 14, 14A, 14B after getting through the gas distributor 27, and contact with the slurry contained in the vessel 1 during the ascending process, and react in the presence of catalyst in the slurry materials. In addition, the ascending of the gas also brings ascending power to the slurry, and accordingly drives the ascending of slurry. The gas reactants ascend to gas-liquid interface 2 while undergoing the reaction, carrying small amount of slurry. They ascend from the opening on the top of reactor vessel 1 and leave the gas-liquid interface 2, and is delivered to the top external circulation apparatus, which is as described above. A portion of the liquid materials (e.g. Ci ₂ -C ₃₀ heavy hydrocarbon) are discharged as a liquid products 6 after getting condensed by condenser 4 and conducting liquid-gas separation by gas-liquid separator 5. The worthless portion of the separated gas is discharged as tail gas 8 while the contained unreacted gas raw materials are compressed by the gas compressor 25 as circulation gas, mixed with fresh gas reactants 26, and re-delivered to gas distributor 27 to conduct circulation reaction. The valuable liquid materials separated from the gas-liquid separator 5, such as solvents or liquid products like C ₅ -Ci ₀ light hydrocarbon, are compressed by circulation pump 10 and heated by optional heater 1 1, and then delivered to the center injector and peripheral injector, respectively, and ejected into the reactor vessel.

Optionally, external circulation is conducted for a portion of liquid materials in the slurry materials beneath the gas-liquid interface 2 by using the middle external circulation apparatus. The invention can be conducted using the middle external circulation apparatus only, or the top external circulation apparatus only, or both the middle external circulation apparatus and the top external circulation apparatus. Preferably, the top external circulation apparatus and the middle external circulation apparatus are used for the external circulation at the same time. In particular, the middle external circulation includes the following: the solid components in the slurry are removed by liquid-solid separator 16 in the reactor, and slurry 17 with low solid content after removing solid is delivered to gas-liquid separator 19 by a pressure relief valve 18. The separated gas is discharged as tail gas 20. Liquid-solid separation operation is further conducted for the slurry phase portion in a secondary liquid-solid separator 21, wherein a portion of separated liquid such as the hydrocarbon products synthesized by a Fischer-Tropsch reaction is drawn as liquid product 22 for further processing and refining treatment. The remaining valuable liquid materials (such as solvents, etc.) is compressed by circulation pump 23 and heated by heater 1 1, and delivered to the center injectors and peripheral injectors, respectively, and ejected into the reactor vessel.

In another aspect, in the reactor vessel 1 , in the presence of ascending gaseous reactants, the slurry materials ascend in the space in the reactor vessel 1 and outside of the center descending pipe 14 to the surroundings of gas-liquid interface 2. After the reacted gaseous materials leave the gas-liquid interface 2, the remaining slurry materials enter the center descending pipe 14 from the top opening of the center descending pipe 14, flow downwardly under the self-gravity of the slurry and the function of center injector 15, and flow out from the opening on the bottom of center descending pipe 14. Now the slurry arrives the upward side of gas distributor 27, and ascends again in the space in the reactor vessel and outside of the center descending pipe driven by the gas reactants. That is to say, the slurry in the reactor vessel 1 ascends outside of the center descending pipe 14, and descends in the center descending pipe, forming internal circulation of slurry in reactor vessel 1.

In conclusion, the present invention provides a gas distributor at the bottom of the reactor vessel, which distributes gas reactant raw materials upwardly into the reactor vessel, provides peripheral injectors along the inner wall of the reactor vessel, and thus can make the slurry ejected obliquely and upwardly and can further promote the ascending of slurry between the inner wall of the reactor vessel and the wall of the center descending pipe, while the downward ejection of center injector pipe in the center descending pipe promotes the descending of slurry in the center descending pipe. At the same time, at least a portion of the slurry materials and/or gas materials are recycled back into the reactor vessel through the external circulation outside the reactor vessel by the middle external circulation apparatus and the top external circulation apparatus. The recycled gases from the external circulation returns back to the reactor and mixed with gaseous reactants and participate in the reaction. The recycled liquid from the external circulation (e.g. C5-C10 light hydrocarbons) continues to return back to the reactor vessel, stirring and suspending the gaseous reactants and the catalyst powders. The combination of the above two actions can enhance particle suspension, liquid-solid mixing, as well as heat transfer and mass transfer in the slurry-bed reactor.

The slurry-bed reactions that can be conducted by using this method are selected from the group consisting of a Fischer-Tropsch reaction, a direct coal liquefaction reaction, a synthesis reaction of dimethyl ether from synthesis gas, and a synthesis reaction of methanol from synthesis gas, preferably a Fischer-Tropsch reaction.

When conducting a Fischer-Tropsch reaction by using the reactor as disclosed in examples herein, the slurry is formed by suspending solid catalysts in hydrocarbon oil, the mixed gas of raw gas CO and hydrogen are reacted in the slurry, generating hydrocarbon products and by-products such as a small amount of water and carbon dioxide. Under this situation, the water and gaseous materials in the slurry are removed by the middle external circulation apparatus through the external circulation process. The hydrocarbon products are separated and recovered, and then the remaining slurry is sent back to the injector. The liquid in the top external circulation apparatus is mainly volatile components with low boiling points, such as C ₅ ~Cio light hydrocarbons. In addition, small amount of heavy fractions that are liquid under the reaction temperature and pressure will also enter into the tail gas system due to entrainment of tail gas in the top of the reactor. Finally, very small amount of heavy fractions will still enter the external circulation liquid flow portion (engineering terminology, flow of substances) after despumation, condensation, phase splitting and dehydration.

According to the design of the present invention, the gaseous reactants and the liquid-solid materials ascend under the effect of the gas distributor in the reactor vessel, reacting and forming the slurry materials in the ascending process. The slurry materials reach the place near the gas-liquid interface. The gas materials keeps ascending, and reach the top region of the reactor vessel. The slurry, with density increased after the up flowing of the gas materials, gets into the center descending pipes from the top opening of the center descending pipes, flows downwardly under its own gravity, flows out from the bottom openings of the center descending pipes, then ascends again in the space in the reactor vessel and outside of the center descending pipes driven by the gas reactants, forming an internal reacting circulation. At the same time, the center injectors and the peripheral injectors are provided in the present invention. The slurry materials ascend outside of the center descending pipes and descend in the center descending pipes under the effect of the peripheral injectors and the center injectors, and thus promoting the internal circulation in the center descending pipes and the reactor vessel. In addition, the slurry materials are sprayed into the reactor vessel after being recycled externally by the top external circulation apparatus and the middle external circulation apparatus. The preferred position and location of the center injectors and the peripheral injectors can realize optimized turbulence effects, enhancing gas-liquid and liquid-solid stirring, and improving particle suspension and liquid-solid circulation. Preferably, the ejecting kinetic energy per unit volume of the slurry is thought only to be necessary to maintain the turbulence required for the reaction. Otherwise, excessive ejecting kinetic energy could result in excessive energy consumption. Meanwhile, it may also cause mechanical vibration of the internal components of the reactor. In exmaples, the external circulation liquid is ejected into the slurry in the reactor from center injectors and peripheral injectors provided according to specific angles and positions. The ejecting kinetic energy per unit volume of liquid is 0.001-0.05 W/m ³ , preferably 0.002-0.04 W/m ³ , for example at least 0.001 W/m ³ , 0.002 W/m ³ , 0.003 W/m ³ , 0.004 W/m ³ , 0. 005 W/m ³ or 0.008 W/m ³ , or for example no more than 0.01 W/m ³ , 0.02 W/m ³ , 0.03 W/m ³ , 0.04 W/m ³ or 0.05 W/m ³ .