Organic hydride dehydrogenation reaction system and method

Abstract

The invention relates to an organic hydride dehydrogenation reaction system and method, and belongs to the field of chemical processes. The system comprises N stages of tubular reactors of which the tube paths are sequentially connected in series and the shell paths are sequentially connected in series, wherein N is greater than or equal to 2; the organic hydride dehydrogenation reaction system further comprises a second heat exchanger E2 and a third heat exchanger E3; the second heat exchanger E2 is composed of a heat exchange pipeline II and a heat exchange pipeline II'which can conduct heat exchange. The third heat exchanger E2 is composed of a heat exchange pipeline III and a heat exchange pipeline III'which can conduct heat exchange. The organic hydride source, the heat exchange pipeline II, the heat exchange pipeline III and a tube pass inlet of the first-stage tubular reactor are communicated in sequence; and a tube pass outlet of the Nth-stage tubular reactor is communicated with a heat exchange pipeline II ', and a shell pass outlet of the Nth-stage tubular reactor is communicated with a heat exchange pipeline III'. According to the invention, the problems of easy coking and deactivation of a dehydrogenation catalyst, insufficient process energy utilization and low product hydrogen concentration at the present stage are mainly solved.

Description

Technical Field

[0001] The invention belongs to the field of chemical technology, and in particular relates to a dehydrogenation method, and specifically relates to an organic hydride dehydrogenation reaction system and method. Background Art

[0002] Hydrogen energy is a green and sustainable new energy with good application prospects. Hydrogen storage and transportation are the key difficulties in the application of hydrogen energy. In recent years, liquid organic hydride hydrogen storage technology based on chemical reaction method has attracted more and more attention due to its advantages such as large hydrogen storage capacity, high energy density, safe and convenient liquid storage and transportation. Through this method, hydrogen can undergo hydrogenation reaction with unsaturated hydrocarbons at the production site and be converted into liquid organic hydrides for transportation. At hydrogen use sites such as hydrogen stations or factories, organic hydrides undergo dehydrogenation reaction to obtain hydrogen and unsaturated hydrocarbons, and then the unsaturated hydrocarbons are transported to the hydrogen production site.

[0003] Dehydrogenation reaction is a strong endothermic reaction, and a large amount of heat needs to be provided by the outside world during the reaction process. Especially for organic hydrides with high hydrogen density, the heat required for the reaction is higher, such as the heat of dehydrogenation of methylcyclohexane reaches 250kJ / mol. Therefore, heat supply is the key to the dehydrogenation process. In most known dehydrogenation processes and production devices, the heat required for the dehydrogenation reaction is brought into the reactor by the reaction raw materials before the reactor and the heat carrier entering the shell side of the reactor. At the entrance of the reactor, the heat of the shell side heat carrier has not been transferred to the tube in time. At this time, the heat required for the dehydrogenation reaction is mainly brought by the reaction raw materials themselves. Under the action of the catalyst, the reaction rate is fast, the reaction heat absorption is large, and the system temperature is rapidly reduced. As the reaction proceeds, the reaction rate slows down, and the heat carried by the shell side heat carrier can be supplied to the tube in time for dehydrogenation reaction. The heat supply rate and the reaction rate maintain a relatively balanced state. At this time, the system temperature gradually increases again, so the catalyst temperature in the tube undergoes a process of abrupt decline and slow rise, and the catalyst near the temperature inflection point is very easy to coke and deactivate.

[0004] US20170015553A1 prevents carbon deposition on the dehydrogenation catalyst by circulating a portion of the hydrogen produced by the dehydrogenation reaction of the organic liquid, thereby inhibiting the reduction of the catalyst activity. Specifically, the hydrogen production system includes a first dehydrogenation reaction unit, which is used to generate hydrogen by dehydrogenation reaction of the organic liquid in the presence of a first catalyst, and a second dehydrogenation reaction unit, which is used to receive the product of the first dehydrogenation reaction unit and generate hydrogen by dehydrogenating the organic liquid remaining in the product in the presence of a second catalyst.

[0005] CN112707368A cools the reaction product of the first reactor and then enters a gas phase separator to separate hydrogen and unreacted products. The unreacted products are then heated up and enter a second reactor for dehydrogenation reaction, thereby avoiding catalyst coking by separating hydrogen.

[0006] Most of the above-mentioned processes maintain stable catalyst performance at the expense of some catalysts or energy consumption, fail to effectively match the reaction rate and heating rate, shorten the catalyst life, insufficiently utilize the system's heat, and increase the cost of hydrogen storage. Summary of the invention

[0007] To solve the above problems, the present invention provides an organic hydride dehydrogenation system and method, which mainly solves the problems of easy coking and deactivation of dehydrogenation catalysts, insufficient process energy utilization and low product hydrogen concentration at the current stage, and has the advantages of long catalyst service life, sufficient system energy utilization, high product hydrogen purity and low total cost.

[0008] On the one hand, the present invention provides an organic hydride dehydrogenation reaction system, comprising N-stage shell-and-tube reactors in which tube sides are sequentially connected in series and shell sides are sequentially connected in series, N≥2; the organic hydride dehydrogenation reaction system also includes a second heat exchanger E2 and a third heat exchanger E3; the second heat exchanger E2 is composed of a heat exchange pipeline II and a heat exchange pipeline II' that can perform heat exchange; the third heat exchanger E2 is composed of a heat exchange pipeline III and a heat exchange pipeline III' that can perform heat exchange; the organic hydride source, the heat exchange pipeline II, the heat exchange pipeline III, and the tube side inlet of the first-stage shell-and-tube reactor are sequentially connected; the tube side outlet of the N-stage shell-and-tube reactor is connected to the heat exchange pipeline II'; the shell side outlet of the N-stage shell-and-tube reactor is connected to the heat exchange pipeline III'.

[0009] The N (N≥2) stages of shell-and-tube reactors described in the present invention are connected in series in the tubes, which means that the tubes of the first stage shell-and-tube reactor, the tubes of the second stage shell-and-tube reactor, ..., the tubes of the nth stage shell-and-tube reactor, the tubes of the n+1th stage shell-and-tube reactor, the tubes of the n+2th stage shell-and-tube reactor, ... the tubes of the N-1th stage shell-and-tube reactor and the tubes of the Nth stage shell-and-tube reactor are connected in series via pipelines. Preferably, the outlet of the tube side of the first-stage shell-and-tube reactor is connected to the inlet of the tube side of the second-stage shell-and-tube reactor via a pipeline..., the outlet of the tube side of the nth-stage shell-and-tube reactor is connected to the inlet of the tube side of the n+1th-stage shell-and-tube reactor via a pipeline, the outlet of the tube side of the n+1th-stage shell-and-tube reactor is connected to the inlet of the tube side of the n+2th-stage shell-and-tube reactor via a pipeline..., the outlet of the tube side of the N-1th-stage shell-and-tube reactor is connected to the inlet of the tube side of the Nth-stage shell-and-tube reactor via a pipeline.

[0010] The N (N≥3) stages of shell-and-tube reactors described in the present invention are shell-side serially connected, which means that: the shell side of the first stage shell-and-tube reactor, the shell side of the second stage shell-and-tube reactor..., the shell side of the nth stage shell-and-tube reactor, the shell side of the n+1th stage shell-and-tube reactor, the shell side of the n+2th stage shell-and-tube reactor,...the shell side of the N-1th stage shell-and-tube reactor, and the shell side of the Nth stage shell-and-tube reactor are sequentially connected via pipelines. Preferably, the shell side outlet of the first-stage shell-and-tube reactor is connected to the shell side inlet of the second-stage shell-and-tube reactor via a pipeline, the shell side outlet of the n-stage shell-and-tube reactor and the shell side inlet of the n+1-stage shell-and-tube reactor are connected via a pipeline; the shell side outlet of the n+1-stage shell-and-tube reactor and the shell side inlet of the n+2-stage shell-and-tube reactor are connected via a pipeline..., the shell side outlet of the N-1-stage shell-and-tube reactor and the shell side inlet of the N-stage shell-and-tube reactor are connected via a pipeline.

[0011] Optionally, a heater H is provided at the shell inlet of the nth stage tube reactor. n ; n = any integer from 1 to N.

[0012] Preferably, the organic hydride dehydrogenation reaction system further comprises a first heat exchanger E1; the first heat exchanger E1 is composed of a heat exchange pipeline I and a heat exchange pipeline I' capable of performing heat exchange; when n=1, the heat carrier source, the heat exchange pipeline I, the heater H1, and the shell side inlet of the first-stage tubular reactor are sequentially connected; the heat exchange pipeline III' is connected to the heat exchange pipeline I'.

[0013] Preferably, the organic hydride dehydrogenation reaction system further comprises a cooler and a gas-liquid separator; the tube-side outlet of the N-stage shell-and-tube reactor is sequentially connected to the heat exchange pipeline II', the cooler and the gas-liquid separator; preferably, the gas phase outlet of the gas-liquid separator is connected to the tube-side inlet of the first-stage shell-and-tube reactor; preferably, the gas phase outlet of the gas-liquid separator has a plurality of branch pipes, wherein at least one branch pipe is connected to the tube-side inlet of the first-stage shell-and-tube reactor.

[0014] Preferably, the organic hydride dehydrogenation reaction system further comprises a cooler, a first gas-liquid separator, a compressor, and a second gas-liquid separator; the tube-side outlet of the N-th stage shell-and-tube reactor is sequentially connected to the heat exchange pipeline II', the cooler and the first gas-liquid separator; the gas phase outlet of the first gas-liquid separator is sequentially connected to the compressor and the second gas-liquid separator; the gas phase outlet of the second gas-liquid separator is connected to the tube-side inlet of the first-stage shell-and-tube reactor; preferably, the gas phase outlet of the gas phase outlet of the second gas-liquid separator has a plurality of branch pipes, wherein at least one branch pipe is connected to the tube-side inlet of the first-stage shell-and-tube reactor.

[0015] Preferably, the ratio of the catalyst loading amount of the n+1th stage tubular reactor to the catalyst loading amount of the nth stage tubular reactor is 0.5 to 1.5, preferably, the ratio is 0.9 to 1.1.

[0016] The catalyst used in the tubular organic hydride dehydrogenation reaction system and method of the present invention is a catalyst commonly used in the dehydrogenation reaction of organic liquid hydrogen storage materials, such as: Pt / Al2O3 composite catalyst, preferably with the addition of auxiliary agents Fe and lanthanide elements, preferably the catalyst prepared by the Chinese invention patent application disclosure specification CN111054383A.

[0017] On the other hand, the present invention also provides a method for dehydrogenating an organic hydride by the organic hydride dehydrogenation reaction system, comprising: a catalyst and an inert ceramic are installed in each tube of the N-stage tube-in-tube reactor; the tubes in the first-stage tube-in-tube reactor are equally divided into M sections along the axial direction, M is an integer, 5≤M≤20, the volume ratio of the catalyst in the Mth section to the catalyst in the M-1st section is R, 1.05≤R≤1.5; each section of the catalyst is uniformly mixed with the inert ceramic; the volume ratio of the catalyst in the second to N-stage tube-in-tube reactors to the volume ratio of the inert ceramic is 1 / Y, 1≤Y≤4, and the catalyst is uniformly mixed with the inert ceramic; the catalyst loading amount of each tube-in-tube reactor is the same; the organic hydride The compound is first vaporized by the second heat exchanger E2, then heated to the initial reaction temperature by the third heat exchanger E3, and then enters the tube side of the first-stage shell-and-tube reactor R1 equipped with catalyst and inert ceramic parts to undergo a dehydrogenation reaction; the n-stage reaction product enters the n+1-stage shell-and-tube reactor to undergo an n-stage reaction; the N-stage reaction product flows through the second heat exchanger E2 as a heat source for E2; the heat carrier enters the shell side of the n-stage shell-and-tube reactor to provide heat for the dehydrogenation reaction in the n-stage tube side; then enters the shell side of the n+1-stage shell-and-tube reactor to provide heat for the dehydrogenation reaction in the n+1-stage tube side; the heat carrier flowing out of the N-stage shell side outlet flows through the third heat exchanger E3 as a heat source for E3.

[0018] Optionally, the ceramic piece is a ceramic ring or a ceramic particle;

[0019] Preferably, 9≤M≤12;

[0020] Preferably, 1.05≤R≤1.3, more preferably 1.2≤R≤1.4

[0021] Preferably, Y=3;

[0022] Optionally, the particle size of the catalyst is 1.8 to 2 mm, and the particle size of the inert ceramic ring is 2 to 5 mm, and they are filled into a cylinder with a height of 3 to 8 mm.

[0023] Optionally, the heat carrier is first preheated by the first heat exchanger E1 and then heated by the first-stage heater H1 before entering the shell side of the first-stage shell-and-tube reactor to provide heat for the dehydrogenation reaction in the tube side.

[0024] Optionally, after the Nth stage reaction product flows out from E2, it passes through a cooler to form a gas-liquid mixture; the gas-liquid mixture is separated to obtain a gas phase and a liquid phase.

[0025] Optionally, the gas-liquid mixture flows through the gas-liquid separation I of the first gas-liquid separator V1 to obtain crude hydrogen and toluene respectively, and the separation pressure is 0.02MPaA~1.0MPaA, which is the outlet pressure of the cooler, and the separation temperature of the gas-liquid separation I is 5~60°C, preferably 35~45°C; the crude hydrogen is compressed at least one stage and then passes through the gas-liquid separation II of the second gas-liquid separator V2 to obtain high-purity product hydrogen and toluene, and the separation pressure is 0.4MPaA~3MPaA, which is the outlet pressure of the compressor connected to the gas-liquid separator, and the separation temperature of the gas-liquid separation II is 5~60°C, preferably 35~45°C; the high-purity product hydrogen is divided into two streams, one of which is used as circulating hydrogen and returned to the tube side of the first-stage reactor.

[0026] Optionally, the compressor outlet pressure is 0.4 MPaA to 3 MPaA, preferably, the pressure is 1.0 MPaA to 2.0 MPaA.

[0027] Optionally, the circulating hydrogen is first merged with the organic hydride and then returned to the tube side of the first-stage reactor; the merging position is before the second heat exchanger E2 or before the third heat exchanger E3 or before the first-stage reactor.

[0028] Optionally, the temperature of the heat carrier at the shell side inlet of the nth stage tube-in-shell reactor is 350-500°C, preferably 400°C.

[0029] Optionally, the temperature of the reactants at the tube side inlet of the n+1th stage shell and tube reactor is 10°C to 60°C higher than the temperature of the reactants at the tube side inlet of the nth stage shell and tube reactor, preferably 15°C to 35°C, preferably 20°C.

[0030] Optionally, the temperature of the reactants at the tube side inlet of the first stage shell-and-tube reactor is 280-320°C, preferably 300°C.

[0031] Optionally, the temperature of the reactants at the tube inlet of the second-stage shell-and-tube reactor is 280-340°C, preferably 320°C.

[0032] Optionally, the temperature of the organic hydride at the tube side inlet of the n-th stage shell-and-tube reactor is 280-380°C.

[0033] Optionally, the temperature of the heat carrier at the inlet of the shell side of the nth stage shell-and-tube reactor is 40°C to 150°C higher than the temperature of the reactants at the inlet of the tube side, preferably 50°C to 120°C.

[0034] Optionally, the organic hydride is selected from at least one of substituted or unsubstituted alkanes, substituted or unsubstituted cycloalkanes, substituted or unsubstituted olefins, substituted or unsubstituted monocyclic aromatic hydrocarbons, and substituted or unsubstituted condensed aromatic hydrocarbons.

[0035] Optionally, the substituted or unsubstituted alkane is selected from at least one of C1-C6 alkanes; preferably propane or butane.

[0036] Optionally, the substituted or unsubstituted cycloalkane is selected from at least one of C3-C6 alkanes; preferably cyclohexane or methylcyclohexane.

[0037] Optionally, the substituted or unsubstituted olefin is selected from at least one of C2-C6 olefin hydrocarbons; preferably butene.

[0038] Optionally, the substituted or unsubstituted monocyclic aromatic hydrocarbon is selected from at least one of ethylbenzene, dibenzyltoluene, cyclohexylbenzene and dicyclohexylbenzene.

[0039] Optionally, the substituted or unsubstituted condensed aromatic hydrocarbon is selected from at least one of tetralin and decalin.

[0040] Optionally, the heat carrier is selected from water vapor or molten salt;

[0041] Optionally, the molten salt is selected from at least one of potassium nitrate, sodium nitrite and sodium nitrate;

[0042] Optionally, the molten salt is preferably composed of potassium nitrate, sodium nitrite and sodium nitrate in a weight ratio of (40-60): (30-50): (5-10);

[0043] Optionally, the molten salt is preferably composed of 53% potassium nitrate, 40% sodium nitrite and 7% sodium nitrate.

[0044] Optionally, the flow direction of the organic hydride in the tube side of the n-th stage tubular reactor is in parallel with the flow direction of the heat carrier in the shell side.

[0045] Optionally, the cooling medium for the reaction product is air or water.

[0046] Optionally, in the tube side of the n-stage tubular reactor, the conditions for the dehydrogenation reaction include: a reaction temperature of 200°C to 500°C, preferably 250°C to 400°C; a reaction pressure of 0.02MPaA to 1.0MPaA, preferably 0.1MPaA to 0.4MPaA; a total mass space velocity of the organic hydride of 0.5h -1 ~5h -1 , preferably 2h -1 ~4h -1The ratio of the flow rate of the heat carrier at the shell side inlet of the first stage shell and tube reactor to the flow rate of the organic hydride at the tube side inlet of the first stage shell and tube reactor is 2 to 5; the total mass space velocity of the organic hydride at the tube side inlet of the first stage shell and tube reactor is 4 to 20 h -1 .

[0047] Optionally, the content of circulating hydrogen in the total gas phase is 5% to 50%, preferably 10% to 20%.

[0048] The present invention introduces inert porcelain balls to optimize the loading amount of the catalyst from top to bottom in the first reactor along the axial direction, so that the loading amount of the catalyst from the inlet to the outlet gradually increases, so that the dehydrogenation reaction has a lower reaction degree and a slower reaction rate due to the small loading amount of the catalyst at the inlet of the first reactor, thereby avoiding a sudden drop in the catalyst temperature. Subsequently, as the reaction rate and the heat supply rate are matched, the catalyst temperature of the entire tube pass is evenly distributed, so that the reaction rate and conversion rate of each reactor are within a reasonable range, greatly improving the service life of the catalyst. In addition, by recovering the heat of the reaction product and the heat carrier, the energy utilization rate of the entire device is greatly increased, and by compressing the crude hydrogen step by step, the purity of the product hydrogen is greatly improved.

[0049] By adopting the technical scheme of the present invention, for a device using methylcyclohexane as a dehydrogenation raw material, the catalyst life is increased by 1 to 2 times, the hydrogen purity is higher than 99.9 vol%, the dehydrogenation cost is reduced by 10%, and good technical effects are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the organic hydride dehydrogenation system of Example 1.

[0051] Figure 1 In the figure, 1 first stage shell and tube reactor R1, 2 second stage shell and tube reactor R2, 3 first heat exchanger E1 (preheater), 4 first stage heater H1, 5 second stage heater H2, 6 second heat exchanger E2 (vaporizer), 7 third heat exchanger E3 (superheater), 8 cooler, 9 first gas-liquid separator V1, 10 compressor, 11 second gas-liquid separator V2;

[0052] 101 organic hydride source, 102 organic hydride vaporized in the first stage heat exchanger, 103 organic hydride overheated in the second stage heat exchanger, 104 reaction product at the outlet of the first stage shell and tube reactor, 105 reaction product at the outlet of the second stage shell and tube reactor; 106 crude hydrogen, 107 toluene, 108 high-purity product hydrogen, 109 high-purity product hydrogen used as circulating hydrogen;

[0053] 111 heat carrier source, 112 heat carrier at the outlet of the first-stage shell-and-tube reactor, 113 heat carrier at the outlet of the second-stage shell-and-tube reactor; 114 heat carrier going out of the boundary.

[0054] Figure 2 This is the temperature distribution diagram of the R1 tube side of Example 2, Figure 2 In the figure, T is the temperature and L is the tube length.

[0055] Figure 3 This is the temperature distribution diagram of the R1 tube side of Example 3, Figure 3 In the figure, T is the temperature and L is the tube length.

[0056] Figure 4 This is the temperature distribution diagram of the R1 tube side of Example 4, Figure 4 In the figure, T is the temperature and L is the tube length.

[0057] Figure 5 This is the temperature distribution diagram of the R1 tube side of Example 5, Figure 5 In the figure, T is the temperature and L is the tube length. DETAILED DESCRIPTION

[0058] The present invention adopts a technical solution in which a heat carrier is heated and enters the shell side of a multi-stage tubular reactor to provide heat for a dehydrogenation reaction in the tube side, and controls the inlet temperature of the tube side of the first-stage reactor and the inlet temperature of the heat carrier of each stage reactor to control the dehydrogenation conversion rate and the dehydrogenation reaction rate of each stage reactor. After the reaction product vaporizes the raw material, it is cooled, gas-liquid separated, pressurized and gas-liquid separated again to obtain high-purity hydrogen. This problem is well solved and can be used in the industrial production of organic hydride hydrogen storage.

[0059] As a preferred embodiment, a method for dehydrogenating an organic hydride using the tubular reactor organic hydride dehydrogenation system of the present invention comprises the following steps:

[0060] a. Catalyst and inert ceramic rings are loaded in the tubes of the tubular reactor;

[0061] Each tube of the N-stage shell-and-tube reactor is filled with catalyst and inert ceramic parts;

[0062] The tubes in the first-stage tube-shell reactor are equally divided into M sections along the axial direction, where M is 5.

[0063] The volume ratio of the Mth stage catalyst to the M-1th stage catalyst is R, and R is 1.05.

[0064] The volume ratio of the catalyst to the volume of the inert ceramic parts in the 2nd to Nth stage shell-and-tube reactors is 1 / Y, Y=3, and the catalyst loading amount in each stage of the shell-and-tube reactor is the same;

[0065] b The organic hydride 101 is first vaporized by the second heat exchanger E2 (vaporizer), and then heated to the initial reaction temperature by the third heat exchanger E3 (superheater), and then enters the tube side of the first-stage shell-and-tube reactor R1 equipped with a catalyst to undergo a dehydrogenation reaction, until it flows out from the tube side of the N-th stage shell-and-tube reactor to obtain a reaction product containing hydrogen, where N≥2; the reaction product containing hydrogen flows through the second heat exchanger E2 (vaporizer) as a heat source of E2, and after flowing out of E2, it passes through a cooler to form a gas-liquid mixture; the gas-liquid mixture flows through the first gas-liquid separator V1 to obtain crude hydrogen 106 and toluene respectively; the crude hydrogen 106 is compressed at least once and then separated by gas and liquid in the second gas-liquid separator V2 to obtain high-purity product hydrogen (108, 109) and toluene; the high-purity product hydrogen is divided into two streams, one of which 109 is used as circulating hydrogen and mixed with the organic hydride 103, and then returned to the tube side of the first-stage reactor;

[0066] c The heat carrier 111 is first preheated by the first heat exchanger E1 (preheater), and then heated by the first stage heater H1, and then enters the shell side of the first stage shell and tube reactor at a position 100mm below the top of the tube, providing heat for the dehydrogenation reaction in the tube side, and then flows out from the shell side outlet of the first stage shell and tube reactor and enters the second stage heater H2 for heating, and then enters the shell side of the second stage shell and tube reactor, until it flows out from the shell side of the N stage shell and tube reactor; the heat carrier at the shell side outlet of the N stage shell and tube reactor is first used as the heat source of the third heat exchanger E3 (superheater) in step 3, and then as the heat source of the first heat exchanger E1 (preheater), and finally merged into the steam network;

[0067] d. Control the temperature of the outlet of the first-stage heater H1 (the temperature of the heat carrier at the inlet of the shell side of the first-stage shell-and-tube reactor); control the temperature after mixing 109 and 103 (the temperature of the tube side of the first-stage shell-and-tube reactor).

[0068] Example 1 Tubular organic hydride dehydrogenation system (taking a two-stage tubular reactor as an example)

[0069] The shell-and-tube organic hydride dehydrogenation reaction system is mainly composed of a first-stage shell-and-tube reactor R1, a second-stage shell-and-tube reactor R2, a first heat exchanger E1 (preheater), a first-stage heater H1, a second-stage heater H2, a second heat exchanger E2, a third heat exchanger E3, a cooler, a first gas-liquid separator V1, a compressor and a second gas-liquid separator V2.

[0070] The tube specifications of R1 and R2 are the same. The length of the tube is 4 meters, the number of tubes is 1000, and the diameter of the shell side (reactor cylinder) is 1200 mm. The inside of the tubes of R1 and R2 are filled with catalysts and inert ceramic rings.

[0071] The first heat exchanger E1 is composed of heat exchange pipelines I and I' for heat exchange; the second heat exchanger E2 is composed of heat exchange pipelines II and II' for heat exchange; the third heat exchanger E3 is composed of heat exchange pipelines III and III' for heat exchange.

[0072] The heat carrier source 111 is connected to the heat exchange pipeline I of the first heat exchanger E1 (preheater), and then connected to the inlet of the first heater H1. The outlet of H1 is connected to the shell side of R1 at a position 100mm below the top of the tubes of R1. The shell side outlet of R1 (located at the lower part of R1, specifically 100mm above the bottom of the tubes) is connected to the inlet of the second heater H2, and the outlet of H2 is connected to the shell side of R2 at a position 100mm below the top of the tubes of R2. The shell side outlet of R2 (located at the lower part of R2, specifically 100mm above the bottom of the tubes) is connected to the heat exchange pipeline III' of the third heat exchanger E3, and heat exchange is performed with the heat exchange pipeline III in E3, and then connected to the heat exchange pipeline I' of the first heat exchanger E1, and heat exchange is performed with the heat exchange pipeline I in E1.

[0073] The organic hydride source 101 is connected to the heat exchange pipeline II of the second heat exchanger E2 (vaporizer), and the heat exchange pipeline III of the third heat exchanger E3 (superheater) in sequence. The heat exchange pipeline III is connected to the pipe inlet of R1 (located at the top of R1) through a pipeline; the pipe outlet of R1 (located at the bottom of R1) is connected to the pipe inlet of R2 (located at the top of R2); the pipe outlet of R2 (located at the bottom of R2) is connected to the heat exchange pipeline II' of the second heat exchanger E2, and heat is exchanged with the heat exchange pipeline II of E2, and then the heat exchange pipeline III is connected to the pipe inlet of R1 (located at the top of R2) through a pipeline; ... The cooler is connected to the first gas-liquid separator V1, the gas phase outlet of the first gas-liquid separator V1 (located at the top of the first gas-liquid separator V1) is connected to the second gas-liquid separator V2 through the compressor, the gas phase outlet of the second gas-liquid separator V1 (located at the top of the second gas-liquid separator V2) is connected to two parallel streams, one of which is connected to the pipe side inlet of R1; the liquid phase outlet of the first gas-liquid separator V1 (located at the bottom of the first gas-liquid separator V1) is connected to the liquid phase outlet of the second gas-liquid separator V2 (located at the bottom of the second gas-liquid separator V2).

[0074] Example 2 Organic hydride dehydrogenation reaction method

[0075] A 1000 ton / year hydrogen plant uses methylcyclohexane as the dehydrogenation raw material and uses the system and Figure 1 The process technology shown in the figure uses 1.0MPaA saturated water vapor as the heat carrier and adopts two-stage compression ( Figure 1 Only the first stage of compression is schematically drawn in the figure), and the main working conditions and operating conditions are shown in Table 1.

[0076] The calculation of methylcyclohexane conversion rate is shown in formula (1):

[0077]

[0078] When calculating the conversion rate of methylcyclohexane in the n-stage reactor, it is calculated according to formula (1), in which m1 is the mass of methylcyclohexane at the inlet of the n-stage reactor, m2 is the mass of methylcyclohexane at the outlet of the n-stage reactor, and n=1~N.

[0079] When calculating the total conversion rate of methylcyclohexane in the shell-and-tube organic hydride dehydrogenation reaction system, it is calculated according to formula (1), where m1 is the mass of methylcyclohexane at the inlet of the first-stage reactor, and m2 is the mass of methylcyclohexane at the outlet of the Nth-stage reactor. In Example 2, N is 2.

[0080] In the embodiment of the present invention, the catalyst is the catalyst prepared in Example 1 of the Chinese invention patent application publication CN111054383A; the composition of the porcelain ball is inert alumina, and the particle size is Purchased from Xiangdong Petrochemical Packing Factory, Pingxiang City, Jiangxi Province.

[0081] Flow direction of heat carrier (steam) in the shell of tubular reactor:

[0082] After being heated by the first-stage heater H1, the heat carrier 108 (water vapor) enters the shell side of R1 at a position 100 mm below the top of the R1 tube, providing heat for the dehydrogenation reaction in the R1 tube side, and then flows out from the shell side outlet of R1 (located at the lower part of R1, specifically 100 mm above the bottom of the tube), and after being heated by the second-stage heater H2, enters the shell side of R2 at a position 100 mm below the top of the R2 tube, and flows out from the shell side outlet of R2 (located at the lower part of R2, specifically 100 mm above the bottom of the tube), flows through the heat exchange pipeline III' of the third heat exchanger E3 (superheater), serving as the heat source of the heat exchange pipeline III of E3, and after flowing out from E3, flows through the heat exchange pipeline I' of the first heat exchanger E1 (preheater), serving as the heat source of the heat exchange pipeline I of E1, and flows out from E1 and is merged into the steam network.

[0083] Flow direction of organic hydride (methylcyclohexane) in R1 and R2 tubes:

[0084] The methylcyclohexane 101 first flows through the heat exchange pipeline II of the second heat exchanger E2, is heated and vaporized by the R2 tube side outlet product 105 in the heat exchange pipeline II' (the vaporization temperature is 145°C), and then flows through the heat exchange pipeline III of the third heat exchanger E3, is heated to the initial reaction temperature (320°C) by the heat carrier 113 in the heat exchange pipeline III', and then merges with 109 and enters the R1 tube side from the R1 tube side inlet (located at the top of R1) to undergo the first stage of dehydrogenation reaction, and the R1 outlet product 104 is discharged from the R1 tube side outlet (located at the bottom of R1). Then, it enters R2 for the second-stage dehydrogenation reaction. The initial reaction temperature of R2 is 340°C. The product 105 containing hydrogen flows out from the outlet of the tube side of R2 (located at the bottom of R2), flows through the heat exchange pipeline II' of the second heat exchanger E2, and serves as the heat source of the heat exchange pipeline II of the second heat exchanger E2; after flowing out of the second heat exchanger E2, it enters the first gas-liquid separator V1 after being cooled by the cooler, and the separation pressure is 0.28MPaA, the outlet pressure of the cooler, and the separation temperature of gas-liquid separation I is 35°C; the gas phase 106 is compressed by the compressor and enters the second gas-liquid separator V2, and the separation pressure is 1.1MPaA, the outlet pressure of the compressor connected to the gas-liquid separator, and the separation temperature of gas-liquid separation II is 35°C; the gas phase of the second gas-liquid separator V1 is divided into two streams, of which 109 and 103 merge and enter the tube side of R1; the liquid phase of the first gas-liquid separator V1 merges with the liquid phase of the second gas-liquid separator V2.

[0085] Table 1

[0086] project Working conditions <![CDATA[Reaction pressure in R1 and R2, MPaA]]> 0.3 <![CDATA[Loading ratio of the catalyst in R2 to the catalyst in R1]]> 1.1 (height) <![CDATA[Number of segments M in R1]]> 5 <![CDATA[Volume ratio of the (M + 1)-th stage catalyst to the M-th stage catalyst in R1]]> 1.05 <![CDATA[Volume ratio of catalyst to inert porcelain rings in R2]]> 3 <![CDATA[The shell-side inlet temperature of R1, °C]]> 440 <![CDATA[The inlet temperature of the shell side of R2, °C]]> 440 <![CDATA[Tube-side inlet temperature of R1, °C]]> 320 <![CDATA[Tube-side inlet temperature of R2, °C]]> 340 <![CDATA[Difference between the inlet temperature and the lowest temperature of the R1 tube side, °C]]> 50 <![CDATA[Conversion rate of methylcyclohexane of R1, %]]> 65.0 <![CDATA[Conversion rate of methylcyclohexane of R2, %]]> 86.0 Total conversion rate of methylcyclohexane, % 95.1 Ratio of circulating hydrogen to product hydrogen, % 20 Steam (heat carrier) consumption, kg / h 12000 Product hydrogen pressure, MPaA 1.1 Product hydrogen concentration, vol% 99.90 Catalyst regeneration cycle, month 24

[0087] Figure 2 This is the temperature distribution diagram of the R1 tube. When the material enters the tube, a dehydrogenation reaction occurs rapidly under the action of the catalyst. The temperature in the tube drops sharply and drops to a minimum of 270°C at 0.2m. Subsequently, as the reaction rate and the heating rate match, the catalyst temperature of the entire tube increases slowly.

[0088] Example 3

[0089] A 1000 ton / year hydrogen plant uses methylcyclohexane as the dehydrogenation raw material and uses the system of Example 1. Figure 1 The process technology shown is the same as the organic hydride dehydrogenation reaction method of Example 2, except that the number of catalyst segments in R1 is changed, and the other process parameters are the same as those of Example 2. The device parameters are listed in Table 2

[0090] Table 2

[0091] project Working conditions <![CDATA[Reaction pressure in R1 and R2, MPaA]]> 0.3 <![CDATA[The number of segments M in R1]]> 20 <![CDATA[Volume ratio of the (M + 1)-th stage catalyst to the M-th stage catalyst in R1]]> 1.05 <![CDATA[Volume ratio of catalyst to inert porcelain rings in R2]]> 3 <![CDATA[The inlet temperature of the shell side of R1, °C]]> 440 <![CDATA[The inlet temperature of the shell side of R2, °C]]> 440 <![CDATA[Tube-side inlet temperature of R1, °C]]> 320 <![CDATA[Tube-side inlet temperature of R2, °C]]> 340 <![CDATA[Difference between the inlet temperature and the lowest temperature of the R1 tube side, °C]]> 40 <![CDATA[Conversion rate of methylcyclohexane of R1, %]]> 68.0 <![CDATA[Conversion rate of methylcyclohexane of R2, %]]> 88.0 Total conversion rate of methylcyclohexane, % 96.1 Ratio of circulating hydrogen to product hydrogen, % 20 Steam (heat carrier) consumption, kg / h 12000 Product hydrogen pressure, MPaA 1.1 Product hydrogen concentration, vol% 99.92 Catalyst regeneration cycle, month 28

[0092] Figure 3It is the temperature distribution diagram of R1 tube side. When the material enters the tube, dehydrogenation reaction occurs rapidly under the action of the catalyst, and the temperature in the tube drops sharply. However, since the number of segments of R1 is more than the number of segments in Example 2, the catalyst loading at the inlet is reduced, and it drops to a minimum of 280°C at 0.2m, which is 10°C higher than the minimum temperature in Example 1. Subsequently, as the reaction rate and the heat supply rate match, the catalyst temperature of the entire tube side increases slowly.

[0093] Example 4

[0094] A 1000 ton / year hydrogen plant uses methylcyclohexane as the dehydrogenation raw material and uses the system of Example 1. Figure 1 The process technology shown is the same as the organic hydride dehydrogenation reaction method of Example 2, the number of catalyst segments in R1 and the volume ratio of the M+1th catalyst segment to the Mth segment in R1 are changed, and the other process parameters are the same as those of Example 2. The device parameters are listed in Table 3

[0095] Table 3

[0096] project Working conditions <![CDATA[Reaction pressure in R1 and R2, MPaA]]> 0.3 <![CDATA[The number of segments M in R1]]> 10 <![CDATA[Volume ratio of the (M + 1)-th stage catalyst to the M-th stage catalyst in R1]]> 1.3 <![CDATA[Volume ratio of catalyst to inert porcelain rings in R2]]> 3 <![CDATA[The inlet temperature of the shell side of R1, °C]]> 440 <![CDATA[The shell-side inlet temperature of R2, °C]]> 440 <![CDATA[Tube-side inlet temperature of R1, °C]]> 320 <![CDATA[Tube-side inlet temperature of R2, °C]]> 340 <![CDATA[The difference between the inlet temperature and the lowest temperature of the R1 tube side, °C]]> 5 <![CDATA[Conversion rate of methylcyclohexane of R1, %]]> 69.0 <![CDATA[Conversion rate of methylcyclohexane of R2, %]]> 91.0 Total conversion rate of methylcyclohexane, % 97.2 Ratio of circulating hydrogen to product hydrogen, % 20 Steam (heat carrier) consumption, kg / h 12000 Product hydrogen pressure, MPaA 1.1 Product hydrogen concentration, vol% 99.98 Catalyst regeneration cycle, month 40

[0097] Figure 4 This is the temperature distribution diagram of the R1 tube. After the volume ratio of the catalyst in the M+1 section to the M section is increased from 1.05 to 1.3, the catalyst loading at the inlet is further reduced. At this time, the reaction degree at the inlet is mild, the reaction rate and the heating rate can be well matched, the lowest temperature is only 315°C, and the temperature distribution of the entire tube is uniform.

[0098] Comparative Example

[0099] A 1000 ton / year hydrogen plant uses methylcyclohexane as the dehydrogenation raw material and uses the system of Example 1. Figure 1 The process technology shown is different from the organic hydride dehydrogenation reaction method of Example 2, except that the catalyst in R1 is not loaded in stages, the heat carrier is 1.0 MPaA saturated water vapor, and a two-stage compression ( Figure 1 Only the first stage of compression is schematically drawn in the figure), and the main working conditions and operating conditions are shown in Table 4.

[0100] Table 4

[0101] project Working conditions <![CDATA[Reaction pressure in R1 and R2, MPaA]]> 0.3 <![CDATA[Volume ratio of catalyst to inert porcelain rings in R1 and R2]]> 3 <![CDATA[The inlet temperature of the shell side of R1, °C]]> 440 <![CDATA[The shell-side inlet temperature of R2, °C]]> 440 <![CDATA[Tube-side inlet temperature of R1, °C]]> 320 <![CDATA[Tube side inlet temperature of R2, ℃]]> 340 <![CDATA[The difference between the inlet temperature and the lowest temperature of the R1 tube side, °C]]> 70 <![CDATA[Conversion rate of methylcyclohexane of R1, %]]> 63.0 <![CDATA[Conversion rate of methylcyclohexane of R2, %]]> 85.0 Total conversion rate of methylcyclohexane, % 94.4 Ratio of circulating hydrogen to product hydrogen, % 20 Steam (heat carrier) consumption, kg / h 13000 Product hydrogen pressure, MPaA 1.1 Product hydrogen concentration, vol% 99.85 Catalyst regeneration cycle, month 20

[0102] Figure 5 This is the temperature distribution diagram of the R1 tube. Since no segmented loading is used, the catalyst loading at the inlet is high. When the material enters the tube, a dehydrogenation reaction occurs rapidly under the action of the catalyst. The temperature in the tube drops sharply, dropping to 290°C at 0.1m and to a minimum of 250°C at 0.2m, which is extremely unfavorable to the stability of the catalyst.

[0103] By comparing with Example 3 and Comparative Example 1, it can be seen that when the technical solution provided by the present invention is adopted, the difference between the inlet temperature and the lowest temperature of the first-stage tubular reactor R1 tube side is reduced from 70°C to 5°C, the catalyst regeneration cycle is increased by 2 times, the steam consumption is reduced by 8%, and the concentration of the obtained product hydrogen is greater than 99.98 vol%, achieving good technical effects.

Claims

1. An organic hydride dehydrogenation reaction system, characterized in that: It includes N-stage tubular reactors with tube sides connected in series and shell sides connected in series, N≥2; The organic hydride dehydrogenation reaction system further includes a second heat exchanger E2 and a third heat exchanger E3; the second heat exchanger E2 is composed of a heat exchange pipeline II and a heat exchange pipeline II' capable of heat exchange; the third heat exchanger E2 is composed of a heat exchange pipeline III and a heat exchange pipeline III' capable of heat exchange; The organic hydride source, the heat exchange pipeline II, the heat exchange pipeline III, and the tube side inlet of the first stage tubular reactor are connected in sequence; The tube outlet of the Nth stage tubular reactor is connected to the heat exchange pipeline II'; The shell side outlet of the Nth stage shell-and-tube reactor is connected to the heat exchange pipeline III'.

2. The organic hydride dehydrogenation reaction system according to claim 1, characterized in that: The shell side inlet of the nth stage tube reactor is provided with a heater H n ; n = any integer from 1 to N; Preferably, the organic hydride dehydrogenation reaction system further comprises a first heat exchanger E1; The first heat exchanger E1 is composed of a heat exchange pipeline I and a heat exchange pipeline I' capable of performing heat exchange; When n=1, the heat carrier source, the heat exchange pipeline I, the heater H1, and the shell side inlet of the first stage tube reactor are connected in sequence; The heat exchange pipeline III' is communicated with the heat exchange pipeline I'.

3. The organic hydride dehydrogenation reaction system according to claim 1 or 2, characterized in that: The organic hydride dehydrogenation reaction system also includes a cooler and a gas-liquid separator; The tube outlet of the Nth stage tubular reactor is connected in sequence to the heat exchange pipeline II', the cooler and the gas-liquid separator; Preferably, the gas phase outlet of the gas-liquid separator is connected to the tube side inlet of the first stage tubular reactor; Preferably, the gas phase outlet of the gas-liquid separator has a plurality of branch pipes, at least one of which is connected to the tube side inlet of the first stage tubular reactor; And / or, the ratio of the catalyst loading amount of the n+1th stage tubular reactor to the catalyst loading amount of the nth stage tubular reactor is 0.5 to 1.5, preferably, the ratio is 0.9 to 1.

1.

4. The organic hydride dehydrogenation reaction system according to claim 1, 2 or 3, characterized in that: The organic hydride dehydrogenation reaction system also includes a cooler, a first gas-liquid separator, a compressor, and a second gas-liquid separator; The tube outlet of the Nth stage tubular reactor is connected in sequence to the heat exchange pipeline II', the cooler and the first gas-liquid separator; The gas phase outlet of the first gas-liquid separator is connected to the compressor and the second gas-liquid separator in sequence; The gas phase outlet of the second gas-liquid separator is connected to the tube side inlet of the first stage tubular reactor; Preferably, the gas phase outlet of the second gas-liquid separator has a plurality of branch pipes, wherein at least one branch pipe is connected to the tube side inlet of the first stage tube-in-tube reactor.

5. A method for dehydrogenating an organic hydride using the organic hydride dehydrogenation reaction system according to any one of claims 1 to 4, characterized in that: include: Each tube of the N-stage tube-shell reactor is filled with a catalyst and an inert ceramic component; The tubes in the first-stage tube reactor are equally divided into M sections along the axial direction, where M is an integer, 5≤M≤20. The volume ratio of the Mth stage catalyst to the M-1th stage catalyst is R, 1.05≤R≤1.5; The volume ratio of the catalyst to the volume ratio of the inert ceramic parts in the 2nd to Nth stage tubular reactors is 1 / Y, 1≤Y≤4; The catalyst loading amount of each stage of tubular reactor is the same; The organic hydride is first vaporized by the second heat exchanger E2, then heated to the initial reaction temperature by the third heat exchanger E3, and then enters the tube side of the first-stage tubular reactor R1 equipped with catalyst and inert ceramic parts to undergo dehydrogenation reaction; the nth-stage reaction product enters the n+1th-stage tubular reactor to undergo nth-stage reaction; the Nth-stage reaction product flows through the second heat exchanger E2 as the heat source of E2; The heat carrier enters the shell side of the n-stage shell-and-tube reactor to provide heat for the dehydrogenation reaction in the n-stage tube side; then enters the shell side of the n+1-stage shell-and-tube reactor to provide heat for the dehydrogenation reaction in the n+1-stage tube side; the heat carrier flowing out of the N-stage shell side outlet flows through the third heat exchanger E3 as the heat source of E3.

6. The method for dehydrogenating an organic hydride according to claim 5, characterized in that: The ceramic parts are ceramic rings or ceramic particles; and / or, 9≤M≤12; and / or, 1.05≤R≤1.3, preferably 1.2≤R≤1.4 and / or, Y=3; and / or, the particle size of the catalyst is 1.8 to 2 mm; and / or, the particle size of the inert porcelain is 2 to 5 mm; The heat carrier is first preheated by the first heat exchanger E1, and then heated by the first-stage heater H1 before entering the shell side of the first-stage shell-and-tube reactor to provide heat for the dehydrogenation reaction in the tube side. Preferably, after the Nth stage reaction product flows out from E2, it passes through a cooler to form a gas-liquid mixture; the gas-liquid mixture is separated to obtain a gas phase and a liquid phase; Preferably, the gas-liquid mixture flows through the gas-liquid separation I of the first gas-liquid separator V1 to obtain crude hydrogen and toluene respectively, and the separation temperature of the gas-liquid separation I is 5-60°C, preferably, 35-45°C; the crude hydrogen is compressed at least one stage and then passes through the gas-liquid separation II of the second gas-liquid separator V2 to obtain high-purity product hydrogen and toluene, and the separation temperature of the gas-liquid separation II is 5-60°C, preferably, 35-45°C; the high-purity product hydrogen is divided into two streams, one of which is used as circulating hydrogen and returned to the tube side of the first-stage reactor; Preferably, the compressor outlet pressure is 0.4 MPaA to 3 MPaA, preferably, the pressure is 1.0 MPaA to 2.0 MPaA; Preferably, the circulating hydrogen first merges with the organic hydride and then returns to the tube side of the first-stage reactor; the merging position is before the second heat exchanger E2 or before the third heat exchanger E3 or before the first-stage reactor; And / or, the temperature of the heat carrier at the shell side inlet of the nth stage tube-in-shell reactor is 350-500°C, preferably 400°C. and / or, the temperature of the reactants at the tube side inlet of the n+1th stage shell-and-tube reactor is 10°C to 60°C, preferably 15°C to 35°C, preferably 20°C higher than the temperature of the reactants at the tube side inlet of the nth stage shell-and-tube reactor; and / or, the temperature of the reactants at the tube side inlet of the first stage shell-and-tube reactor is 280-320° C., preferably 300° C.; and / or, the temperature of the reactants at the tube side inlet of the second stage shell-and-tube reactor is 280-340° C., preferably 320° C.; and / or, the temperature of the organic hydride at the tube side inlet of the n-th stage shell-and-tube reactor is 280-380° C.; And / or, the temperature of the heat carrier at the inlet of the shell side of the n-th stage shell-and-tube reactor is 40°C to 150°C higher than the temperature of the reactants at the inlet of the tube side, preferably 50°C to 120°C.

7. The method for dehydrogenating an organic hydride according to claim 5 or 6, characterized in that: The organic hydride is selected from at least one of substituted or unsubstituted alkanes, substituted or unsubstituted cycloalkanes, substituted or unsubstituted olefins, substituted or unsubstituted monocyclic aromatic hydrocarbons, and substituted or unsubstituted condensed aromatic hydrocarbons; Preferably, the substituted or unsubstituted alkane is selected from at least one of C1-C6 alkanes; preferably propane or butane; And / or, the substituted or unsubstituted cycloalkane is selected from at least one of C3-C6 alkanes; preferably cyclohexane or methylcyclohexane; And / or, the substituted or unsubstituted olefin is selected from at least one of C2-C6 olefin hydrocarbons; preferably butene; And / or, the substituted or unsubstituted monocyclic aromatic hydrocarbon is at least one selected from ethylbenzene, dibenzyltoluene, cyclohexylbenzene, and dicyclohexylbenzene; and / or, the substituted or unsubstituted condensed aromatic hydrocarbon is selected from at least one of tetralin and decalin; And / or, the heat carrier is selected from water vapor or molten salt; preferably, the molten salt is selected from at least one of potassium nitrate, sodium nitrite and sodium nitrate; preferably, the molten salt is preferably composed of potassium nitrate, sodium nitrite and sodium nitrate in a weight ratio of (40-60): (30-50): (5-10); preferably, the molten salt is preferably composed of 53% potassium nitrate, 40% sodium nitrite and 7% sodium nitrate.

8. The method for dehydrogenating an organic hydride according to any one of claims 5 to 7, characterized in that: The flow direction of the organic hydride in the tube side of the n-stage tubular reactor is in parallel with the flow direction of the heat carrier in the shell side; And / or, the cooling medium for the reaction product is air or water.

9. The method for dehydrogenating an organic hydride according to any one of claims 5 to 8, characterized in that: In the tube side of the nth stage tubular reactor, the conditions for the dehydrogenation reaction include: The reaction temperature is 200°C to 500°C, preferably 250°C to 400°C; The reaction pressure is 0.02MPaA to 1.0MPaA, preferably 0.1MPaA to 0.4MPaA; The total mass space velocity of organic hydride is 0.5h -1 ~5h -1 , preferably 2h -1 ~4h -1 ; The ratio of the flow rate of the heat carrier at the shell side inlet of the first stage shell and tube reactor to the flow rate of the organic hydride at the tube side inlet of the first stage shell and tube reactor is 2 to 5; The total mass space velocity of organic hydride at the tube inlet of the first stage tubular reactor is 4 to 20 h -1 .

10. The method for dehydrogenating an organic hydride according to any one of claims 5 to 9, characterized in that: The content of circulating hydrogen in the total gas phase is 5% to 50%, preferably 10% to 20%.

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