Medium and low temperature coal tar hydrodistillation reactor and hydroprocessing system using the reactor

Abstract

The present invention discloses a medium- and low-temperature coal tar hydrodistillation reactor and a hydroprocessing system. The reactor includes: a reaction chamber, inside which there is a catalyst bed arranged in a ring shape. The medium- and low-temperature coal tar after dehydration and impurity removal treatment and the preheated hydrogen feed are in reverse contact in the catalyst bed to carry out hydrocracking reactions; a stripping chamber, which is located in the middle of the hydrodistillation reactor and is a gas phase channel that runs through the reactor vertically. The gas phase products after the hydrocracking reactions in each layer of the catalyst bed enter this gas phase channel under the action of countercurrent hydrogen carrying and stripping, so that the gas phase products can leave the reaction zone in time; a distillation chamber, which is arranged at the upper part of the hydrodistillation reactor, and the gas phase products are rectified and separated in this distillation chamber. The present invention can effectively improve the resource utilization degree of medium- and low-temperature coal tar and increase the yield of target products; at the same time, it can effectively slow down the coking and blocking phenomena of the catalyst bed and extend the operation cycle of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical hydrogenation reaction, and particularly relates to a medium and low temperature coal tar hydrogenation distillation reactor and a hydrogenation treatment system using the reactor. Background Art

[0002] Coal tar is one of the liquid products obtained during the coking and gasification processes of coal. According to different cracking temperatures, it can be divided into several different products such as low temperature coal tar (450 - 550°C), medium temperature coal tar (600 - 800°C), and high temperature coal tar (1000°C). Among them, the composition and properties of medium and low temperature coal tar are different from those of high temperature coal tar. It has relatively more saturated hydrocarbons and is more suitable for achieving the purpose of improving the stability of coal tar, reducing sulfur content and aromatic content under the action of hydrogen and catalyst, so as to obtain clean fuel oil products.

[0003] Coal tar generally contains moisture and mechanical impurities. During the hydrogenation treatment process, a high water content can cause problems such as fluctuations in reaction temperature, affected product quality, a decrease in the activity and strength of the catalyst due to long-term contact with water, and corrosion of the distillation tower by hydrogen sulfide and ammonia dissolved in water. Moreover, the mechanical impurities in coal tar are prone to sedimentation when heated to high temperatures, blocking distillation equipment and pipelines. Therefore, coal tar must be dehydrated and de - impurified before entering the hydrogenation equipment. After dehydration and de - impurity treatment, the coal tar undergoes pretreatment processes such as distillation pretreatment, delayed coking pretreatment, ebullated bed pretreatment, and suspension bed, and then enters the fixed - bed hydrogenation process to produce clean fuel oil. Currently, the most commonly used method is to use a distillation tower for pretreatment before hydrogenation feed. The light components obtained from distillation are sent to the hydrogenation unit for hydrogenation treatment, and the obtained heavy components are used as heavy raw material oil components, and the resource utilization is not sufficient. At the same time, distillation pretreatment is a physical process and cannot hydrogenate diolefins and oxides generated by high - temperature cracking, and cannot directly ensure the stable operation of the subsequent hydrogenation process flow.

[0004] Chinese Patent Application CN103059981A discloses a method for hydrogenating coal tar. Coal tar with high contents of impurities, resins, asphaltenes, and oxygen elements is pumped into a pre - hydrogenation reactor for hydrogenation pretreatment. After filtering to separate the fine impurities suspended in the produced oil, it successively undergoes hydro - demetallization and deep hydro - refining reactions. After the water and light components are separated from the reaction - generated material flow, it enters a hydro - cracking reactor and then passes through a distillation device to cut out gasoline fractions, diesel, and hydro - cracking tail oil. Among them, the pre - hydrogenation reactor is filled with two different specifications of substances, maintaining a fixed - bed layer of metal cages and particulate catalysts, and the particulate catalysts are located in the space formed by the metal cages. Although this prior - art solution can ensure the long - term stable operation of the device, the proportion of light components after distillation pretreatment is not high, and the resources are not fully utilized.

[0005] Therefore, there is an urgent need for a hydrodistillation reactor for medium and low temperature coal tar and a system using this reactor, which can not only improve the utilization degree of process technology resources for producing clean fuel oil from medium and low temperature coal tar, but also increase the depth of the hydrogenation reaction and the yield of target products.

[0006] The information disclosed in this background section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0007] The purpose of the present invention is to provide a hydrodistillation reactor for medium and low temperature coal tar and a hydroprocessing system using this reactor. Through the improvement of the internal structure of the hydrodistillation reactor, the utilization degree of resources of medium and low temperature coal tar can be effectively improved, and the yield of target products can be increased; at the same time, the coking and blockage phenomena of the catalyst bed can be effectively alleviated, and the operation cycle of the device can be prolonged.

[0008] After a large number of studies by the inventors, it is found that for the gas-liquid-solid three-phase reaction process in which the liquid phase amount decreases rapidly and the gas phase amount increases rapidly during the reaction, due to the rapid increase in the gas phase amount, a large amount of bed voids are occupied, resulting in a significant increase in the liquid phase flow rate. According to the traditional design, although sufficient contact between the gas, liquid and solid phases can be ensured, the effective reaction time of the liquid phase that needs to be further converted is reduced, and the contact probability between the gas phase that does not need to react again (such as the gas phase obtained by the conversion of the liquid phase under the reaction conditions) and the catalyst increases. For a system that requires more conversion of the liquid phase and control of the secondary reaction of the gas phase, the overall reaction effect is limited to a certain extent, generally manifested as difficulties in further improving the reaction conversion rate, selectivity, etc.

[0009] Based on the above research, to achieve the purpose of the present invention, according to the first aspect of the present invention, a hydrodistillation reactor for medium and low temperature coal tar is provided, comprising: a reaction chamber, in which a catalyst bed arranged in a ring shape is provided, and the medium and low temperature coal tar after dehydration and impurity removal treatment and the preheated hydrogen feed are in reverse contact in the catalyst bed to carry out hydrocracking reaction; a stripping chamber, which is located in the middle of the hydrodistillation reactor and is a gas phase channel that penetrates the reactor up and down. The gas phase products after the hydrocracking reaction of each layer of the catalyst bed enter this gas phase channel under the countercurrent hydrogen carrying and stripping effects, so that the gas phase products can leave the reaction zone in time; a distillation chamber, which is arranged in the upper part of the hydrodistillation reactor, and the gas phase products are rectified and separated in this distillation chamber.

[0010] The inventors further found through research that in the gas-liquid-solid three-phase hydrogenation reaction where the liquid phase volume in the reaction process rapidly decreases and the gas phase volume rapidly increases when the overall space velocity is similar, when the hydrogen gas contacts the raw material oil and gas in a liquid-gas countercurrent manner, the diameter-to-height ratio of the catalyst bed layer in the reactor is significantly higher than that of the existing conventional technology. This enables the generated gas phase to quickly leave the catalyst bed layer, and the cumulative effect of the adverse effects of the generated gas phase is small. The liquid phase has a more sufficient chance to react on the catalyst, thereby overcoming the traditional understanding that a small diameter-to-height ratio would bring about adverse effects such as poor contact effect, achieving the effect of significantly improving the yield of the target product, and at the same time solving problems such as easy flooding in the countercurrent reactor and limited hydrogen-oil ratio.

[0011] Based on the above research, further, in the above technical solution, the diameter-to-height ratio of the catalyst bed layer can be set to 3:1 to 6:1, and the medium and low-temperature coal tar and the catalyst are in a thin-film contact.

[0012] Further, in the above technical solution, a conical gas-liquid diversion plate is provided in the stripping chamber, and the number and position of the gas-liquid diversion plates are matched with the catalyst bed layer.

[0013] Further, in the above technical solution, the hydrodistillation reactor may further include a heavy oil tank, which is communicated with the stripping chamber and receives the liquid phase product after the hydrocracking reaction.

[0014] Further, in the above technical solution, a coal tar distributor, which is in a ring-shaped tube form or a ring-shaped belt form and is arranged above the uppermost catalyst bed layer, and a hydrogen gas feed distributor, which is in a ring-shaped tube form or a ring-shaped belt form and is arranged at the lower part of each catalyst bed layer, can be provided in the reaction chamber.

[0015] Further, in the above technical solution, the hydrogen gas feed distributor can be arranged in a relatively closed space.

[0016] Further, in the above technical solution, a gas diversion unit can be provided between the hydrogen gas feed distributor and the bottom of the catalyst bed layer. The gas diversion unit includes: a diversion plate, which is arranged at the bottom of the catalyst bed layer and is used to receive the liquid phase product after the hydrocracking reaction from the catalyst bed layer; diversion tubes, which are uniformly arranged on the diversion plate and divert the hydrogen gas feed upward to the catalyst bed layer, and a first cap is provided at the top of the diversion tubes; an overflow weir, which is close to the stripping chamber side and is used to overflow the liquid phase product on the diversion plate to the next catalyst bed layer.

[0017] Further, in the above technical solution, a liquid redistribution plate in a ring shape with uniformly opened through holes can be provided below the overflow weir.

[0018] Further, in the above technical solution, the liquid redistribution tray may include: an overflow ring disposed around the top of the through hole for uniformly guiding the liquid-phase product to the next catalyst bed; a baffle disposed on the side away from the stripping chamber, and the upper edge of the baffle is higher than the overflow ring.

[0019] Further, in the above technical solution, the overflow ring may include: a serrated portion bent downward from the outer edge of the through hole toward the center; a drainage groove disposed on the serrated portion and opened along the center of the serrated portion.

[0020] Further, in the above technical solution, air holes are formed on the conical surface of the conical gas-liquid diversion tray, and a second cap is provided at the top of the air holes; the gas-phase product after the hydrocracking reaction rises from the air holes and converges into the distillation chamber, and part of the heavy component liquid-phase product drips onto the gas-liquid diversion tray and flows back to the reaction chamber.

[0021] Further, in the above technical solution, the distillation chamber may include a mixing section and a separation section, and a packing or a tray is provided in the separation section.

[0022] Further, in the above technical solution, the cross-sectional area ratio of the distillation chamber to the stripping chamber may be 1:1 to 8:1; the cross-sectional area ratio of the stripping chamber to the reaction chamber may be 1:4 to 1:20.

[0023] Further, in the above technical solution, the number of catalyst beds may be one or more; the catalyst is a cylindrical bar, a clover, a four-leaf clover, a Raschig ring or a honeycomb porous special-shaped catalyst; the porosity of the catalyst bed is 20% to 75%.

[0024] Further, in the above technical solution, the operating conditions of the coal tar hydrocracking reaction process in the hydrodistillation reactor are as follows: the reaction temperature is 300°C to 400°C, the reaction pressure is 10 MPa to 20 MPa, the hydrogen-oil volume ratio is 200:1 to 800:1, and the volume space velocity is 0.2 h-1 to 2.0 h-1.

[0025] According to the second aspect of the present invention, the present invention provides a hydrotreating system using the aforementioned hydrodistillation reactor; the lightest component separated by the distillation chamber flows out from the top of the hydrodistillation reactor, and after being purified by a top condenser and a hydrogen purification system, hydrogen is recovered and used as recycle hydrogen, and the liquid condensed by the top condenser returns to the distillation chamber; other light components flow out from the side line and sequentially enter a hydrofining reactor, a high-pressure separator, a low-pressure separator, and a product fractionation tower, and naphtha fraction and diesel fraction are fractionated, and the tail oil returns to the reaction chamber of the hydrodistillation reactor.

[0026] Furthermore, in the above technical solution, the reaction temperature of the hydrotreating reactor can be 320°C to 450°C, the reaction pressure is 8MPa to 20MPa, the hydrogen-oil volume ratio is 600:1 to 1200:1, and the volume space velocity is 0.2h-1 to 3.0h-1.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention uses a hydrodistillation reactor to pre-distill coal tar and uses a lower reaction temperature to hydrocracking the heavy oil fraction. The heavy oil fraction is further converted to lighter oil through hydrocracking, thereby improving the resource utilization of coal tar.

[0029] (2) Compared with the traditional hydrocracking reactor, the hydrodistillation reactor of the present invention adopts a "blade" type catalyst bed with a higher bed diameter-to-height ratio, which can make the reaction more complete; the raw oil can enter each catalyst bed layer by layer, and when a bed cannot work normally due to problems such as blockage, the raw oil can directly enter the next catalyst bed by passing through the bed baffle, effectively avoiding the problem of increased bed pressure drop or even shutdown caused by bed blockage that is prone to coal tar, and the device operation is more stable and the operation cycle is longer;

[0030] (3) During the hydrogenation process of the present invention, the light components of the distillate oil after hydrogenation can quickly leave the system, which can increase the forward reaction rate, so that the hydrogenation reaction can also achieve a higher reaction rate at a lower reaction temperature. At the same time, the heat generated by the hydrogenation reaction can also leave the reaction bed along with the light components, preventing the bed from overheating. The lower reaction temperature, and the fact that the products and heat can quickly leave the reaction system, reduce the condensation reaction of polycyclic aromatic hydrocarbons and reduce the hidden danger of catalyst clogging;

[0031] (4) The present invention can realize the timely extraction of light intermediate products through the stripping effect by setting the stripping chamber, so as to effectively control the reaction degree; at the same time, since the product partial pressure is always kept at a low state, the reaction speed is accelerated, which is beneficial to improving the reaction efficiency and removing undesirable components such as hydrogen sulfide, water and ammonia;

[0032] (5) The coal tar distributor and liquid redistribution plate of the present invention can disperse the passing liquid into small droplets, and with the help of the distillation chamber, the lighter part is directly taken away from the reaction chamber and enters the distillation chamber, while the heavier part enters the hydrocracking reaction zone downward under the action of gravity.

[0033] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and be implemented according to the content of the specification, and in order to make the above and other objects, technical features, and advantages of the present invention more understandable, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings as follows. Description of the Drawings

[0034] Figure 1 is a schematic diagram of the internal structure of the hydrodistillation reactor of the present invention.

[0035] Figure 2 is a bottom view schematic diagram of the first embodiment of the coal tar / hydrogen feed distributor of the present invention.

[0036] Figure 3 is a side view schematic diagram of the coal tar / hydrogen feed distributor of the present invention.

[0037] Figure 4 is a bottom view schematic diagram of the second embodiment of the coal tar / hydrogen feed distributor of the present invention.

[0038] Figure 5 is a bottom view schematic diagram of the liquid redistributor tray of the present invention.

[0039] Figure 6 is a side view schematic diagram of the liquid redistributor tray of the present invention.

[0040] Figure 7 is a three-dimensional structure schematic diagram of the overflow ring in the liquid redistributor tray of the present invention.

[0041] Figure 8 is a structure schematic diagram of the conical gas-liquid deflector tray of the present invention.

[0042] Figure 9 is a structure schematic diagram of the gas deflector unit of the present invention.

[0043] Figure 10 is a process flow schematic diagram of the medium and low temperature coal tar hydrotreating system of the present invention.

[0044] Main reference numeral description:

[0045] 1 - Hydrodistillation reactor; 2 - Hydrofining reactor; 3 - High-pressure separator; 4 - Low-pressure separator; 5 - Fractionating tower; 61 - First hydrogen purifier, 62 - Second hydrogen purifier; 7 - Top condenser; 8 - Liquid separation tank; 9 - Reboiler; 10 - Control valve;

[0046] a - Reaction chamber; b - Distillation chamber; c - Stripping chamber; d - Heavy oil storage bin;

[0047] 101 - Coal tar inlet pipe; 102 - Hydrogen inlet pipe; 103 - Coal tar distributor; 301 - Coal tar feed pipe; 302 - Coal tar distribution pipe; 303 - Hole; 304 - Coal tar distribution tray; 104 - First catalyst bed; 105 - Second catalyst bed; 106 - Hydrogen distribution chamber; 107 - Liquid redistribution tray; 702 - Overflow ring; 7021 - Serrated part; 7022 - Drainage groove; 703 - Through hole; 704 - Baffle; 108 - Gas diversion unit; 801 - First cap; 802 - Diversion hole; 803 - Diversion pipe; 109 - Hydrogen distributor; 110 - Bed baffle; 111 - Gas-liquid diversion tray; 1101 - Second cap; 1102 - Air hole; 1103 - Diversion tray overflow ring; 112 - Overflow weir; 113 - Outer wall of drainage groove; 114 - Drainage groove, 115 - Separation section; 116 - Stabilization section; 117 - First extraction line; 118 - Second extraction line; 119 - Third extraction line; 120 - Mixing section. Detailed implementation manners

[0048] The following will describe in detail the specific implementation manners of the present invention with reference to the accompanying drawings. It should be understood that the protection scope of the present invention is not limited by the specific implementation manners.

[0049] Unless otherwise clearly stated, in the whole specification and claims, the term "comprise" or its variations such as "comprises" or "including" etc. will be understood to include the stated elements or components, without excluding other elements or other components.

[0050] In this article, for convenience of description, spatial relative terms such as "below", "beneath", "under", "above", "over", "on" etc. may be used to describe the relationship between one element or feature and another element or feature in the drawings. It should be understood that the spatial relative terms are intended to cover different directions of the object in use or operation in addition to the directions shown in the drawings. For example, if the object in the drawing is flipped, the element described as "below" or "under" another element or feature will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both the lower and upper directions. The object can also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used herein should be interpreted accordingly.

[0051] In this article, terms such as "first", "second" etc. are used to distinguish two different elements or parts, rather than to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second" etc. can also be interchanged with each other.

[0052] As Figure 1As shown in the figure, the hydrodistillation reactor of the present invention includes a reaction chamber a, a distillation chamber b, a stripping chamber c, and a heavy oil storage d. Among them, an annular catalyst bed is provided in the reaction chamber a. The catalyst bed can be set to one layer or multiple layers. The medium and low-temperature coal tar and hydrogen feedstock are in reverse contact in the catalyst bed, that is, the coal tar enters the catalyst bed of each layer from top to bottom, and the hydrogen feedstock enters from the bottom of the catalyst bed of each layer from bottom to top. The stripping chamber c is located in the middle of the hydrodistillation reactor 1 and is a gas phase channel that runs through the hydrodistillation reactor 1 up and down. The gas phase products after the hydrogenation reaction of each catalyst bed enter this gas phase channel under the carrying and stripping action of the countercurrent gas (i.e., hydrogen), and can quickly leave the reaction system. The distillation chamber b is arranged at the upper part of the hydrodistillation reactor. The gas phase products are rectified and separated in this distillation chamber. The distillation chamber b can include a mixing section 120, a separation section 115, and a stabilization section 116 from bottom to top. The separation section 115 can be provided with 1 to 3 product side lines, such as Figure 1 the first draw line 117, the second draw line 118, and the third draw line 119 shown in

[0053] It should be noted here that: by adopting the structural design of the reverse contact of gas-liquid feedstock and the independent gas phase channel of the stripping chamber in the present invention, the catalyst bed can choose the "blade" type thickness design, that is, the diameter-height ratio of the catalyst bed is 3:1 to 6:1. The diameter-height ratio is the ratio of the diameter to the height of each catalyst bed. In the present invention, the stripping chamber c is in the middle of the reaction chamber a and is not filled with catalyst. For the convenience of description, the present invention still describes it in terms of the diameter-height ratio, which does not affect the understanding of the present invention. This blade-type catalyst bed has a large reaction specific surface area, and the reactants can be evenly contacted. The medium and low-temperature coal tar and the catalyst are in a film-type contact, which can greatly reduce the mass transfer resistance of hydrogen entering the catalyst pores and improve the reaction efficiency. In the existing hydroreactors, the catalyst is "immersed" in the raw oil, and the hydrogen is not evenly distributed in the raw oil. That is to say, the oil film thickness between a part of the hydrogen and the catalyst will be larger. Obviously, a higher hydrogen partial pressure is required in the prior art to achieve the ideal effect, objectively increasing the energy consumption and hydrogen consumption.

[0054] In the catalyst bed of the present invention, a hydrocracking catalyst is used. When the porosity of the catalyst is less than 30%, a catalyst fixing net should be set. When the porosity of the catalyst is ≥30%, the catalyst fixing net may not be set. The catalyst bed can be set with n layers, where n≥1. Different active catalysts can be placed in each catalyst bed, or different active catalysts can be placed in different catalyst beds. The catalyst can be selected from conventional cylindrical bars, clovers, four-leaf clover catalysts, or can also be porous shaped catalysts such as Raschig rings or honeycombs. The pore diameter of the porous catalyst is 1 - 50 mm, preferably 4 - 20 mm; the average particle diameter of the shaped catalyst is 2 - 50 mm, preferably 4 - 30 mm; the pore diameter or pore side length of the honeycomb catalyst is 1 - 50 mm, preferably 3 - 15 mm. The porosity of the catalyst layer is 15% - 85%. The shape of the hydrocracking catalyst carrier can be honeycombs made of ceramic materials, Pall rings, Raschig rings, Intalox saddles, saddles, open-ring types, half rings, cascade rings, double arcs, Hiflow rings, conjugate rings, flat rings, flower rings, hollow spheres and other packings or other porous carriers.

[0055] The hydrocracking catalyst filled in the hydrodistillation reactor contains Y-type zeolite, alumina, and at least one metal component selected from Group VIII metals and at least one metal component selected from Group VIB metals. In the above two catalysts, the Group VIB metals are all selected from molybdenum and / or tungsten, and the Group VIII metals are all selected from cobalt and / or nickel. The metal composition is by weight percentage: tungsten oxide 10% - 30%, nickel oxide 5% - 15%. It may contain a certain amount of molecular sieves, such as one or two of Y-type molecular sieves and β molecular sieves. Generally, it may contain 1% - 30% of molecular sieves, and the rest are refractory tungsten oxide carriers such as amorphous silica-alumina, silica-alumina-containing alumina, and alumina. The pore volume of the catalyst is 0.10 - 0.50 ml / g, and the specific surface area is 120 - 350 m 2 / g.

[0056] Furthermore, as Figure 1 shown, the coal tar distributor 103 of the present invention is arranged above the uppermost catalyst bed and is in the form of a ring-shaped tube or a ring-shaped belt. The coal tar distributor 103 is connected to the coal tar inlet pipe 101. The uppermost catalyst bed includes a first catalyst bed 104 and a second catalyst bed 105. The specific structure of the ring-shaped tube coal tar distributor 103 can refer to Figure 2 and Figure 3 . The coal tar distributor 103 includes a coal tar feed pipe 301 and a coal tar distribution pipe 302. The coal tar distribution pipe 302 is provided with holes 303. Medium and low-temperature coal tar enters the distributor from the coal tar feed pipe 301 and uniformly flows onto the catalyst bed through the holes 303 of the multi-layer tubular coal tar distribution pipe 302 distributed around the stripping chamber. The ring-shaped belt coal tar distributor can refer to Figure 4, The feedstock oil uniformly enters the catalyst bed from the orifices of the distribution tray 304 around the stripping chamber. The orifice diameter of the coal tar distributor 103 can be 1 mm to 20 mm.

[0057] The hydrogen feed distributor 109 of the present invention can also adopt the same structure as the coal tar distributor 103, refer to Figures 2 - 4 . The hydrogen feed distributor 109 is connected to the hydrogen inlet pipe 102. The hydrogen inlet pipe 102 has branch pipes equivalent to the number of catalyst beds, that is, Figure 1 the branch pipes 102-1 to 102-n in Figure 1 . The hydrogen feed distributor 109 is arranged at the lower part of each catalyst bed, preferably arranged in a relatively enclosed space at the lower part of each catalyst bed, that is,

[0058] Further as shown in Figure 1 and Figure 9 , a gas diversion unit 108 is provided between the hydrogen feed distributor 109 and the bottom of the catalyst bed. The gas diversion unit 108 can include a diversion plate, a diversion pipe 803 and an overflow weir 112. The diversion plate is arranged at the bottom of the catalyst bed, and is used to receive the liquid phase product after the hydrocracking reaction of the catalyst bed and divert the hydrogen feed upward; the diversion pipes 803 are uniformly arranged on the diversion plate and divert the hydrogen feed upward to the catalyst bed through the diversion holes 802. A first cap 801 is provided at the top of the diversion pipe 803; the overflow weir 112 is close to the stripping chamber side, and is used to overflow the liquid phase product on the diversion plate to the next catalyst bed. The gas diversion unit 108 can not only divert the hydrogen feed upward into the catalyst bed, but also receive the liquid phase product after the reaction of the current catalyst bed and overflow it to the diversion trough 114 through the overflow weir 112. The liquid phase product and the incompletely reacted coal tar feed then enter the catalyst bed of the next layer. The height of the overflow weir 112 is lower than the height of the diversion pipe 803 and a first cap 801 is arranged at the top of the diversion pipe 803, so that the liquid phase product flowing from top to bottom will not flow into the hydrogen diversion pipe 803, but only flow onto the diversion plate and then flow to the catalyst bed of the next layer through the overflow weir 112. Preferably but not limitedly, the opening ratio of the diversion plate is 5% to 90%, the diameter of the diversion hole 802 is 5 mm to 100 mm, the height of the diversion pipe 803 is 20 mm to 500 mm, and the height difference between the overflow weir 112 and the diversion pipe 803 is 50 to 200 mm. Just keep the first cap 801 directly above the diversion hole 802.

[0059] Before the liquid-phase product enters the next catalyst bed through the overflow weir 112, liquid redistribution can be carried out. The liquid-phase product and the unreacted feedstock oil flow downward from the catalyst bed into the aforementioned gas diversion unit, and the space between the diversion pipes 803 is filled with liquid. When the liquid level is higher than the height of the overflow weir 112, the liquid flows from the overflow weir 112 to the diversion trough 114 and enters the annular liquid redistribution tray 107 of the present invention. As Figure 5 , 6 shown, a plurality of through holes 703 are uniformly formed in the liquid redistribution tray 107 of the present invention. An overflow ring 702 is provided above the through holes 703. The overflow ring is arranged around the top of the through holes 703 and is used to uniformly guide the liquid-phase product to the next catalyst bed. A baffle 704 is arranged on the side away from the stripping chamber. The upper edge of the baffle 704 is higher than the overflow ring 702. Further as Figure 7 shown, the overflow ring 702 may be provided with a serrated portion 7021 and a drainage groove 7022. The serrated portion 7021 can be bent downward from the outer edge of the through hole towards the center; the drainage groove 7022 can be arranged on the serrated portion 7021 and opened along the center of the serrated portion.

[0060] Further as Figure 1 and Figure 8 shown, a conical gas-liquid diversion tray 111 can be arranged in the stripping chamber c. Air holes 1102 are formed on the conical surface of the gas-liquid diversion tray 111, and a second cap 1101 is provided at the top of the air holes 1102. The gas-phase product after the hydrocracking reaction rises from the air holes 1102 and converges into the distillation chamber b. Part of the heavy component liquid-phase product drips onto the gas-liquid diversion tray 111 and flows back to the reaction chamber a. Preferably but not restrictively, the apex angle of the conical gas-liquid diversion tray 111 is greater than 60° and less than 180°, and generally should be greater than 90° to increase the gas-phase channel space. The opening ratio of the gas-liquid diversion tray 111 is 5% - 99%. The diameter of the air holes 1102 can be 5 mm - 100 mm, and the height of the diversion tray overflow ring 1103 is 1 mm - 30 mm.

[0061] Furthermore, the hydrodistillation reactor of the present invention can be in the embodiment as Figure 1 shown, with a conical gas-liquid diversion tray 111 arranged in the stripping chamber c; or the gas-liquid diversion tray 111 can be not arranged, and the gas-phase product directly enters the independent gas-phase channel of the stripping chamber c from the reaction zone and then flows upward into the distillation chamber b. One to three light raw material side lines (not shown in the figure) can be arranged in the mixing section 120 of the distillation chamber b, and one to three product side lines are provided in the separation section 115 (see the first extraction line 117, the second extraction line 118, and the third extraction line 119 in Figure 1 ); One to three sections of packing reaction zones (not shown in the figure) can also be arranged in the separation section 115. The non-condensable gas after rectification is discharged from the top of the distillation chamber b. Further, the unreacted heavy fraction in the reaction chamber a converges into the heavy oil tank d at the bottom.

[0062] The hydrodistillation reactor 1 of the present invention adopts a blade-type catalyst bed with a relatively high diameter-to-height ratio, which has a large reaction specific surface area and is arranged in a multi-layer "blade" interval arrangement form, enabling the reactants to come into uniform contact. Moreover, the raw oil and hydrogen are in countercurrent contact within the catalyst bed. Under the action of the countercurrent gas carrying and stripping, the gaseous reaction products quickly leave the reaction system, and the unreacted medium and low-temperature coal tar immediately enters the next "blade" catalyst bed. Similarly, the light components leave the reaction system, and the unreacted raw oil enters the next catalyst bed, and the stepwise reaction is carried out in sequence. Therefore, the yield of the target product can be greatly increased, and the reaction depth can be effectively controlled.

[0063] As Figure 10 shown, the present invention also provides a hydrotreating system using the aforementioned hydrodistillation reactor. The following describes the hydrotreating process of medium and low-temperature coal tar using the system of the present invention: The medium and low-temperature coal tar after dehydration and impurity removal directly enters the reaction chamber a of the hydrodistillation reactor 1 and is evenly sprayed on the catalyst bed at the top layer of the hydrodistillation reactor 1 under the action of the coal tar distributor 103. At the same time, the heated hydrogen H1 is sent into the reaction chamber a of the hydrodistillation reactor 1 and uniformly moves upward from the bottom of each reaction zone under the action of the hydrogen distributor 109 in the reaction chamber a, and countercurrently contacts the raw oil sprayed from the top in the catalyst bed of the first-stage hydrotreating reactor 104 / 105. Under the operating pressure of 10 - 20 MPa, the raw oil and hydrogen carry out a moderate cracking reaction in the catalyst bed of the reactor. Under the action of the cracking catalyst, a part of the long-chain molecules in the coal tar break into short-chain molecules, and a part of the polycyclic aromatic hydrocarbons also break their rings. The smaller hydrocarbon molecules enter the stripping chamber c together with hydrogen and then enter the distillation chamber b together.

[0064] Furthermore, through the separation in the distillation chamber b, the lightest component H2 flows out from the top of the distillation chamber b, is purified by the top condenser 7, the liquid separation tank 8, and the first hydrogen purifier 61, and the recycled hydrogen is recovered for use, and the liquid condensed by the top condenser 7 returns to the distillation chamber b. Other light components L2 flow out from the side line and sequentially enter the hydrofining reactor 2 (to obtain L3), the high-pressure separator 3 (to obtain L4), the low-pressure separator 4 (to obtain L5), and the product fractionating tower 5 (to obtain L6 and L7), and clean fuel oil products, namely naphtha product L6 and diesel product L7, are fractionated, and the tail oil L8 returns to the reaction chamber a of the hydrodistillation reactor.

[0065] The hydrogenated heavy components generated in the reaction chamber a of the hydrodistillation reactor flow downward into the next catalyst bed of the hydrodistillation reactor in sequence, and finally flow into the heavy oil tank d. The liquid phase reflux part L9 of the heavy oil tank of the hydrodistillation reactor is heated by the reboiler 9 and then returned as a raw material to the reaction chamber a of the hydrodistillation reactor. Part of the liquid phase products L10 that are too poor are discharged from the system to improve the properties of the reflux material. The circulation ratio of the bottom heavy oil to the feedstock oil is 1:3 to 10:1. When a certain catalyst bed of the hydrodistillation reactor is blocked, the liquid phase products do not have to pass through the blocked catalyst bed, but directly enter the next catalyst bed through the channel between the bed baffle 110 and the outer wall 113 of the diversion groove, and the hydrogenation system operates normally.

[0066] The invention effects of using the system of the present invention to produce clean fuel oil by hydrogenating coal tar are further illustrated through specific embodiments below. The embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0067] The experimental methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0068] Example 1

[0069] Reference Figure 1As shown, the feedstock oil in this embodiment is medium- and low-temperature coal tar, and its properties are shown in Table 1. The dehydrated and de-impurified coal tar is heated to 320 °C and then enters the reaction chamber a of the hydrodistillation reactor 1. Under the action of the coal tar distributor, it is evenly sprayed onto the catalyst bed at the top layer of the hydrodistillation reactor. At the same time, the heated hydrogen H1 moves uniformly upward from the bottom of each reaction zone under the action of the hydrogen distributor 109, and countercurrently contacts the feedstock oil sprayed from the top in the catalyst bed 104 / 105 of the first-stage hydrogenation reactor. The operating temperature is 340 °C, the operating pressure is 10 MPa, the hydrogen-oil ratio is 800:1, the volumetric space velocity is 1.0 h-1, and the feedstock oil and hydrogen undergo a moderate cracking reaction in the catalyst bed of the reactor. Under the action of the cracking catalyst, some long-chain molecules of the coal tar break into short-chain molecules, and some polycyclic aromatic hydrocarbons also undergo ring cleavage. The smaller hydrocarbon molecules enter the stripping chamber c together with hydrogen and then enter the distillation chamber b together upward. After separation in the distillation chamber b, the lightest components flow out from the top of the distillation chamber b, and the hydrogen is recovered as recycle hydrogen after being purified by the top condenser and the hydrogen purifier. The liquid condensed by the top condenser 7 returns to the distillation chamber b. Other light components L2 flow out from the side line and enter the hydrofining reactor 2, the high-pressure separator 3, the low-pressure separator 4, and the product fractionating column 5 in sequence, and clean fuel oil products, namely naphtha products and diesel products, are fractionated, and the tail oil returns to the reaction chamber a of the hydrodistillation reactor. The reaction temperature of the hydrofining reactor is 370 °C, the operating pressure is 14 MPa, the hydrogen-oil ratio is 800:1, and the volumetric space velocity is 1.0 h-1.

[0070] The hydrocracking heavy components generated in the reaction chamber a of the hydrodistillation reactor sequentially enter the next catalyst bed of the hydrodistillation reactor downward and finally flow into the heavy oil storage tank d. Part of the liquid-phase reflux of the heavy oil storage tank of the hydrodistillation reactor is heated by the reboiler and returned to the reaction chamber a of the hydrodistillation reactor as feedstock, and part of the liquid-phase products that are too poor are discharged from the system to improve the properties of the reflux material.

[0071] In this embodiment, there is no packing reaction zone in the distillation chamber b of the hydrodistillation reactor, and a conical gas-liquid diversion plate 111 is arranged in the stripping chamber c. The coal tar distributor 103 adopts an annular belt distributor, and the diameter of the holes 303 on the distributor is 3 mm. 20 layers of catalyst beds are placed in the reaction chamber a, the catalyst is of Raschig ring property, the diameter is 4 mm, the bed voidage is 51%, and the diameter-height ratio is 5:1. The hydrogen feed distributor 109 adopts an annular tube distributor, and the hole diameter is 4 mm. The height of the diversion tube 803 on the gas diversion unit 108 is 50 mm, and the height of the overflow weir 112 is 30 mm. The diameter of the air holes 1102 in the conical gas-liquid diversion plate 111 is 30 mm, and the height of the diversion plate overflow ring 1103 is 20 mm. The opening rate of the liquid redistribution plate 107 is 85%, the diameter of the through holes 703 is 20 mm, and the height is 15 mm. The distribution areas of the hydrogen feed distributor 109 and the coal tar distributor 103 account for 95% of the bed distribution area.

[0072] The process of this embodiment is as follows: The coal tar raw material enters the reaction chamber a through the inlet pipe 101 and enters the catalyst bed through the coal tar distributor 103; hydrogen enters the hydrogen feed distributor 109 in the reaction chamber a from the hydrogen inlet pipe 102 through the branch pipes 102-1 to 102-20, and then enters the catalyst bed upward, contacting the downward coal tar raw material in a countercurrent manner. The light components generated by the hydrocracking reaction flow from the stripping chamber c to the distillation chamber b. During the flow process, some components are absorbed by the downward droplets for further separation, and finally naphtha fractions (i.e., the first extraction line 117) are produced in the separation section 115. The heavy components flow to the heavy oil tank d and are sent out as products from the bottom outlet.

[0073] The properties of the raw materials in this embodiment are shown in Table 1, and the product distribution and properties are shown in Table 2.

[0074] Example 2

[0075] This embodiment is the same as Embodiment 1, except that the system operating temperature is 330 °C. The product properties are shown in Table 2.

[0076] Example 3

[0077] This embodiment is the same as Embodiment 1, except that the system operating temperature is 350 °C. The product properties are shown in Table 2.

[0078] Example 4

[0079] This embodiment is the same as Embodiment 1, except that the system operating temperature is 340 °C and the hydrogen-oil ratio is 700:1. The product properties are shown in Table 2.

[0080] Comparative Example 1

[0081] A conventional pre-distillation treatment - hydrofining process is adopted. Both the pre-distillation and hydrofining reactors use conventional equipment. After the raw materials are cut by the pre-distillation tower to obtain light components, they enter the hydrofining reactor together with hydrogen, and the reaction process flows from top to bottom in a co-current manner. In the comparative example, the distillation tower splitting temperature is 370 °C, the catalyst loaded in the refining reactor is the same as that in Embodiment 1, and the volume ratio is 1:1. The tail oil full-circulation process is adopted, and the tail oil is intermittently discharged. The remaining process conditions are the same as those in Embodiment 1.

[0082] Properties of the feedstock oil in Table 1

[0083] Item Data Group composition, % Data Density, g / cm3 1.0881 Saturates 17.1 Viscosity / mm2 / s 26.8 Aromatics 22.17 Sulfur content, vol% 0.56 Resins 42.01 Nitrogen content, % 0.98 Asphaltenes 11.72 Carbon residue value, % 14.05 Total metals, μg / g 215.44

[0084] Product distribution and product properties of the examples and comparative examples in Table 2

[0085]

[0086] The foregoing description of specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many changes and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the present invention, as well as various different selections and changes. Any simple modifications, equivalent changes, and modifications made to the above exemplary embodiments shall fall within the protection scope of the present invention.

Claims

1. A medium and low temperature coal tar hydrodistillation reactor, characterized in that, Comprising: A reaction chamber, inside which there is a catalyst bed arranged in a ring shape. The medium and low-temperature coal tar after dehydration and impurity removal and the preheated hydrogen feed are in reverse contact in the catalyst bed for hydrocracking reaction; the diameter-height ratio of the catalyst bed is 3:1 to 6:1, and the medium and low-temperature coal tar and the catalyst are in film-type contact; in the reaction chamber, there are arranged: a coal tar distributor, which is arranged above the uppermost catalyst bed and is in a ring-shaped tube type or ring-shaped belt type; a hydrogen feed distributor, which is arranged at the lower part of each catalyst bed and is in a ring-shaped tube type or ring-shaped belt type; the hydrogen feed distributor is arranged in a relatively enclosed space; A stripping chamber, which is located in the middle of the hydrodistillation reactor and is a gas phase channel that penetrates the reactor vertically. The gas phase products after the hydrocracking reaction of each catalyst bed enter this gas phase channel under the action of countercurrent hydrogen carrying and stripping; A distillation chamber, which is arranged at the upper part of the hydrodistillation reactor, and the gas phase products are rectified and separated in this distillation chamber.

2. The mid- and low-temperature coal tar hydrodistillation reactor according to claim 1, characterized in that, In the stripping chamber, there is a conical gas-liquid diversion plate, and the number and position of the gas-liquid diversion plates are matched with the catalyst bed.

3. The mid- and low-temperature coal tar hydrodistillation reactor according to claim 1, characterized in that, The hydrodistillation reactor further includes a heavy oil storage tank, which is communicated with the stripping chamber and receives the liquid phase products after the hydrocracking reaction.

4. The middle and low temperature coal tar hydrodistillation reactor according to claim 1, characterized in that, Between the hydrogen feed distributor and the bottom of the catalyst bed, there is a gas diversion unit, which includes: A diversion plate, which is arranged at the bottom of the catalyst bed and is used to receive the liquid phase products after the hydrocracking reaction of the catalyst bed; Diversion pipes, which are uniformly arranged on the diversion plate and divert the hydrogen feed upward to the catalyst bed. A first cap is arranged at the top of the diversion pipes; An overflow weir, which is close to the side of the stripping chamber and is used to overflow the liquid phase products on the diversion plate to the next catalyst bed.

5. The mid- and low-temperature coal tar hydrodistillation reactor according to claim 4, characterized in that, Below the overflow weir, there is a liquid redistribution plate in a ring shape and uniformly provided with through holes.

6. The middle and low temperature coal tar hydrodistillation reactor according to claim 5, characterized in that, The liquid redistribution plate includes: An overflow ring, which is arranged around the top of the through holes and is used to uniformly guide the liquid phase products to the next catalyst bed; A baffle, which is arranged on the side far from the stripping chamber, and the upper edge of the baffle is higher than the overflow ring.

7. The mid- and low-temperature coal tar hydrodistillation reactor according to claim 6, wherein, The overflow ring includes: A serrated part, which is bent downward from the outer edge of the through hole towards the center; A drainage groove, which is arranged on the serrated part and is opened along the center of the serrated part.

8. The middle and low temperature coal tar hydrodistillation reactor according to claim 2, wherein, On the conical surface of the conical gas-liquid diversion plate, there are through holes, and a second cap is arranged at the top of the through holes; the gas phase products after the hydrocracking reaction rise from the through holes and converge into the distillation chamber, and part of the heavy component liquid phase products drip onto the gas-liquid diversion plate and flow back to the reaction chamber.

9. The middle and low temperature coal tar hydrodistillation reactor according to claim 1, characterized in that, The distillation chamber includes a mixing section and a separation section, and there are fillers or trays in the separation section.

10. The hydrogenation distillation reactor for medium and low temperature coal tar according to claim 1, characterized in that, The cross-sectional area ratio of the distillation chamber to the stripping chamber is 1:1 to 8:1; the cross-sectional area ratio of the stripping chamber to the reaction chamber is 1:4 to 1:

20.

11. The middle and low temperature coal tar hydrodistillation reactor according to claim 1, characterized in that, The number of catalyst beds is one layer or multiple layers; the catalyst is a cylindrical strip, three-leaf, four-leaf, Raschig ring or honeycomb porous special-shaped catalyst; the porosity of the catalyst bed is 20% to 75%.

12. The mid-low temperature coal tar hydrodistillation reactor according to claim 1, characterized in that, The operating conditions for the coal tar hydrocracking reaction process in the hydrodistillation reactor are as follows: the reaction temperature is 300°C to 400°C, the reaction pressure is 10 MPa to 20 MPa, the hydrogen-oil volume ratio is 200:1 to 800:1, and the volume space velocity is 0.2 h-1 to 2.0 h-1.

13. A hydrotreating system, characterized in that, Use the hydrodistillation reactor described in any one of claims 1 to 12; the lightest component separated by the distillation chamber flows out from the top of the hydrodistillation reactor, and after being purified by the top condenser and the hydrogen purification system, the hydrogen is recovered and used as recycle hydrogen. The liquid condensed by the top condenser returns to the distillation chamber; other light components flow out from the side line and enter the hydrofining reactor, high-pressure separator, low-pressure separator, and product fractionation tower in sequence, and naphtha fraction and diesel fraction are fractionated, and the tail oil returns to the reaction chamber of the hydrodistillation reactor.

14. The hydrotreating system according to claim 13, wherein The reaction temperature of the hydrofining reactor is 320°C to 450°C, the reaction pressure is 8 MPa to 20 MPa, the hydrogen-oil volume ratio is 600:1 to 1200:1, and the volume space velocity is 0.2 h-1 to 3.0 h-1.

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