Particle fischer-tropsch reactor based on diverging graded thermal conduction structure

Abstract

The application provides a granular Fischer-Tropsch reactor based on a diverging and gradually changing heat conduction structure, comprising a cylindrical reaction tube, and a filling section arranged in the center of the reaction tube; the filling section comprises a diverging and gradually changing heat conduction structure arranged at the axis of the reaction tube and granules filling the gap between the diverging and gradually changing heat conduction structure; the diverging and gradually changing heat conduction structure extends from the center to the edge to form a radial heat conduction channel and construct a multi-stage heat dissipation path, the center of the diverging and gradually changing heat conduction structure is the 0th layer containing four branches, each branch is branched twice, and each layer of branches is uniformly distributed along the outer diameter, wherein, H n is the distance from the starting end of the (n+1)th layer to the starting end of the nth layer, R n is the distance from the starting end of the nth layer to the outer edge of the diverging and gradually changing heat conduction structure, W n is the width of the nth layer. The application effectively controls the temperature of the reactor while ensuring other key performances and improving the conversion rate of the target product.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive structure design, specifically a granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermally conductive structure. Background Technology

[0002] Tubular fixed-bed reactors are one of the most successfully used reactor types, simple to install and operate, but have poor heat transfer capacity and large pressure drop. Fischer-Tropsch synthesis is a process that uses syngas as a feedstock to synthesize liquid hydrocarbons or hydrocarbons under appropriate conditions and with a catalyst. However, it releases a large amount of heat during the reaction, with an adiabatic temperature rise of approximately 1750 K. In Fischer-Tropsch synthesis, due to the target product, the ideal temperature should not be too high, as excessively high temperatures can lead to catalyst deactivation and decreased selectivity for long-chain hydrocarbons. Therefore, reducing the reactor bed temperature is crucial for catalyst activity and the selectivity of the target product. Other strongly exothermic reactions require efficient heat transfer from the reactor to ensure temperature uniformity within the reactor. Similarly, strongly endothermic reactions require efficient transfer of externally supplied heat to the reactor.

[0003] In addition, to avoid high pressure drop in industrial-grade reactors, relatively large particles are usually required. Therefore, the design of the heat transfer structure also needs to take into account the impact on particle packing. Summary of the Invention

[0004] In order to solve the problems of the prior art, the present invention provides a structure that can enhance the heat transfer of a Fischer-Tropsch synthesis particle fixed-bed reactor, effectively controlling the reactor temperature while ensuring other key performances, and improving the conversion rate of its target product.

[0005] This invention provides a granular Fischer-Tropsch reactor based on a bifurcated gradient thermal conductivity structure, comprising a cylindrical reaction tube with a filling section at its center. The reactor is connected to three gas mass flow controllers, a preheating mixer, a condenser, a flash tower, a gas-liquid separator, and a secondary condenser. The filling section includes a bifurcated gradient thermal conductivity structure located at the axis of the reaction tube and particles filling the gaps between the bifurcated gradient thermal conductivity structure. The bifurcated gradient thermal conductivity structure extends from the center to the edge, forming radial thermal conduction channels and constructing a multi-stage heat dissipation path. The central layer of the bifurcated gradient thermal conductivity structure is a layer 0 containing four branches, each branch according to… , The system performs secondary branching, with each layer of branches evenly distributed along the outer diameter, where H... n R is the distance between the starting point of layer (n+1) and the starting point of layer n. n W is the distance from the starting end of the nth layer to the outer edge of the bifurcation-based heat-conducting structure. nThis represents the width of the nth layer. The width of each branch is halved to ensure the consistency of the thermally conductive structure volume and to ensure that the particle packing volume remains constant.

[0006] This heat dissipation structure, along its axial direction, rapidly conducts heat from different locations within the catalyst bed through a continuous, highly thermally conductive material, extending radially upwards to the catalyst bed and thus expanding the heat dissipation area. This internal component is made of 13-8Mo stainless steel, a material that does not interfere with the Fischer-Tropsch synthesis reaction, and has a thermal conductivity of 21.3. .

[0007] Further improvements include a cylindrical reaction tube with an inner diameter of 36 mm and a length of 120 mm, and a maximum outer diameter of 32 mm and a length of 58.5 mm for the bifurcated, gradually changing heat-conducting structure. This ensures a gap between the structure and the reactor's inner wall to prevent damage from thermal expansion stress.

[0008] In a further improvement, the thermally conductive structure based on bifurcation gradient has H0=8mm, R0=16mm, α0=0.5, R1=8.88mm, W0=1.2mm, and W1=0.6mm.

[0009] As a further improvement, inert particles are installed at both ends of the catalyst filling region. The addition of the heat-conducting structure will occupy a portion of the volume, but we can ensure that the volume of the filling region remains unchanged by adjusting the amount of inert particles. The volume of the extended catalyst filling section is equal to the volume of the corresponding heat-conducting component.

[0010] In a further improvement, the reactor is filled with a 2mm cobalt-based Fischer-Tropsch synthesis catalyst.

[0011] The reactor is heated to a constant temperature of 490K by electric heating of the walls. The inlet gases are carbon monoxide, hydrogen, and nitrogen at a speed of 0.05 m / s, with molar concentrations of 2.5 mol / m³. 3 5mol / m 3 2.5mol / m 3 .

[0012] The beneficial effects of this invention are as follows:

[0013] 1. It can enhance the heat transfer structure of the Fischer-Tropsch synthesis particle fixed-bed reactor, effectively control the reactor temperature while ensuring other key performances, and improve the conversion rate of its target product.

[0014] 2. The problems of excessively high temperature and uneven temperature distribution in the fixed bed of Fischer-Tropsch synthesis particles have been solved.

[0015] 3. The problem of high pressure drop in the Fischer-Tropsch synthesis reactor has been solved. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a reactor model for the Fischer-Tropsch synthesis particle fixed bed used in this invention.

[0018] Figure 2 The geometric dimensions used in this invention are based on a bifurcated gradient thermal conductive structure.

[0019] Figure 3 The temperature distribution at the center of the example and the comparative example are shown in the diagram.

[0020] Figure 4 This is a comparison of the pressure drop data between the example and the comparative example.

[0021] Figure 5 This is a comparison of the conversion rates of C5+ products in the examples and comparative examples. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] This invention employs a granular Fischer-Tropsch reactor based on a bifurcated gradient thermal conductivity structure, comprising a cylindrical reactor with an inner diameter of 36 mm and a bifurcated gradient thermal conductivity structure. This thermal conductivity structure is installed at the axis of the cylindrical reactor, with a maximum outer diameter of 32 mm, ensuring a gap between the thermal conductivity structure and the wall surface to avoid damage from thermal expansion. The 0th layer of this bifurcated gradient thermal conductivity structure contains four branches, each 1.2 mm wide. Each branch is divided into two sub-branches in the middle, according to… , Therefore, when α0 = 0.5, H0 = 8mm, R1 = 8.88mm, and the width of the first layer branch is half that of the second layer branch, which is 0.6mm. This is to ensure the consistency of the internal component volume. Each layer of branches is evenly distributed along the outer diameter, as shown in the reference. Figure 2 The included angles are γ=90° and β=45°.

[0025] A cylindrical reaction tube with a diameter of 36 mm was used as the Fischer-Tropsch synthesis reactor, containing 2 mm porous spherical catalyst particles and a thermally conductive structure. The catalyst loading volume inside the reactor was [missing information]. To ensure that the catalyst loading volume remains unchanged after the addition of the thermally conductive structure, the packing section should be extended by 4.5 mm. The temperature distribution map taken at the center of the reactor reflects the uniformity of the bed temperature distribution.

[0026] Steady-state calculations were performed by combining a real particle packing model with a thermally conductive structure model based on bifurcation gradient. The reaction conditions for Fischer-Tropsch synthesis in the simulation were as follows: wall temperature and reactant gas inlet temperature were 490 K, reactant gas inlet velocity was 0.05 m / s, and the molar concentrations of carbon monoxide, hydrogen, and nitrogen were 2.5 mol / m³. 3 5mol / m 3 2.5mol / m 3 After convergence, the carbon monoxide conversion rate of the reactor is calculated by obtaining the molar concentration of carbon monoxide at the outlet. The average C5+ selectivity of the reactor was calculated by obtaining the C5+ selectivity of the particulate phase. .

[0027] ;

[0028] ;

[0029] ,in, .

[0030] The conversion rate of C5+ products is affected by and Joint influence. .

[0031] Comparative Example 1

[0032] Based on Example 1, the bifurcation-based gradient heat conduction structure was removed, while the other conditions remained unchanged.

[0033] Comparative Example 2

[0034] Based on Example 1, the heat-conducting structure is replaced with a vertical heat-conducting structure without branching, while all other conditions remain unchanged.

[0035] Comparative Example 3

[0036] Based on Example 1, the two-layer structure based on the bifurcated gradient heat conduction structure is increased to three layers. Two sub-branches are added in the middle of the first layer bifurcation, with H1=4.8mm, R2=6.4mm, w2=0.3mm, and θ=22.5°. All other conditions remain unchanged.

[0037] The internal temperature distribution of the reactor is shown in the figure. Figure 3 Bed pressure drop Figure 4 The conversion rate of the target product is shown in [reference needed]. Figure 5 .

[0038] Depend on Figure 3 It can be seen that the particle Fischer-Tropsch reactor described in this invention has a more uniform bed temperature distribution compared to Comparative Example 1 and Comparative Example 2. Compared to Comparative Example 1, the temperature difference is reduced by 17.98 K, a decrease of 62.13%, and compared to Comparative Example 2, the temperature difference is reduced by 1.78 K, a decrease of 13.97%.

[0039] Depend on Figure 4 It can be seen that the pressure drop of the particle Fischer-Tropsch reactor described in this invention is reduced by 8.6 Pa compared to Comparative Example 1, and by 29.2 Pa compared to Comparative Example 1.

[0040] Depend on Figure 5 It can be seen that the C5+ target product conversion rate of the particle Fischer-Tropsch reactor described in this invention is improved, increasing by 6.89% compared to the comparative example, 4.52% compared to comparative example 2, and 4.76% compared to comparative example 3.

[0041] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, for the device embodiments, the above descriptions are merely preferred embodiments of the present invention. Since they are fundamentally similar to the method embodiments, the descriptions are relatively simple, and relevant parts can be referred to the descriptions of the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, without departing from the principle of the present invention, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermal conductivity structure, characterized in that: It includes a cylindrical reaction tube with a filling section in the center; the filling section includes a bifurcated heat-conducting structure located at the axis of the reaction tube and particles filling the gaps of the bifurcated heat-conducting structure. The bifurcated gradient heat-conducting structure extends from the center to the edge, forming radial heat-conducting channels and constructing a multi-level heat dissipation path. The central layer of the bifurcated gradient heat-conducting structure is the 0th layer, which contains four branches. Each branch follows... , The system performs secondary branching, with each layer of branches evenly distributed along the outer diameter, where H... n R is the distance between the starting point of layer (n+1) and the starting point of layer n. n W is the distance from the starting end of the nth layer to the outer edge of the bifurcation-based heat-conducting structure. n Let α0 be the width of the nth layer, and α0 = 0.

5.

2. The granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermal conductivity structure according to claim 1, characterized in that: The cylindrical reaction tube is a cylindrical container with an inner diameter of 36 mm and a length of 120 mm, and the maximum outer diameter of the bifurcated heat-conducting structure is 32 mm.

3. The granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermal conductivity structure according to claim 1, characterized in that: In the bifurcation-gradient thermal conductive structure, H0=8mm, R0=16mm, R1=8.88mm, W0=1.2mm, and W1=0.6mm.

4. The granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermal conductivity structure according to claim 1, characterized in that: The length of the bifurcation-gradient thermal conductive structure is 58.5 mm.

5. The granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermal conductivity structure according to claim 1, characterized in that: The reactor is filled with a 2 mm cobalt-based Fischer-Tropsch synthesis catalyst.

6. The granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermal conductivity structure according to claim 5, characterized in that: The catalyst is filled with inert particles at both ends of its filling region.

7. The granular Fischer-Tropsch reactor based on a bifurcated, gradually varying thermal conductivity structure according to claim 1, characterized in that: The bifurcation-gradient heat-conducting structure is made of 13-8Mo stainless steel with a thermal conductivity of 21.3 W / (m·K).

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