External-heating fixed-bed oil shale pyrolysis reactor

Abstract

The present invention belongs to the field of oil shale pyrolysis reactors, and particularly relates to an externally heated fixed-bed oil shale pyrolysis reactor, which comprises a shell (1), a heat transfer plate (2) and internal components (3); the internal components (3) successively include a conical diffuser section (301), a cylindrical gradually expanding section (302) and a flow guide cone (303) from top to bottom; the gas outlet of the flow guide cone (303) is fixedly connected to the gas inlet of the cylindrical gradually expanding section (302); the gas outlet of the cylindrical gradually expanding section (302) is fixedly connected to the gas inlet of the conical diffuser section (301); and a flow guide air inlet (304) is arranged on the conical diffuser section (301) and the cylindrical gradually expanding section (302). The present invention can accelerate the discharge of pyrolysis products generated by the pyrolysis of oil shale, avoid the large accumulation and secondary cracking of volatile gases in the reactor, and is beneficial to improving the pyrolysis rate and tar yield.

Description

Technical Field

[0001] The present invention belongs to the field of oil shale pyrolysis reactors, and particularly relates to an externally heated fixed-bed oil shale pyrolysis reactor. Background Art

[0002] In industries such as oil refining, petrochemicals, and chemical engineering, fixed-bed reactors are commonly used reaction process equipment. Fixed-bed reactors have the ability to handle corrosive and toxic gases at high temperatures and pressures, and are widely used in fields such as petrochemical engineering and biochemical engineering. When the fixed-bed reactor operates, it is externally heated at high temperatures, and the heat is transferred to the oil shale. After being heated at high temperatures, the oil shale will undergo pyrolysis. Due to uneven temperature transfer, the degree of pyrolysis of the oil shale is the strongest, the porosity is the largest, and the pressure is the smallest near the heating wall surface and the heat transfer plate. Most of the pyrolysis products will flow to the place with low pressure, that is, near the heating wall surface. The convective heat transfer degree of the innermost layer of oil shale decreases, and the pyrolysis speed is also relatively slow. Secondary cracking of the pyrolysis products will also occur near the heating wall surface, reducing the tar yield. Summary of the Invention

[0003] The present invention aims to overcome the deficiencies of the prior art and provides an externally heated fixed-bed oil shale pyrolysis reactor that can accelerate the discharge of pyrolysis products generated by the pyrolysis of oil shale, avoid the large accumulation and secondary cracking of volatile gases in the reactor, and is beneficial to improving the pyrolysis rate and tar yield.

[0004] To solve the above technical problems, the present invention is implemented as follows:

[0005] The externally heated fixed-bed oil shale pyrolysis reactor includes a housing, a heat transfer plate, and internal components; the internal components are vertically and fixedly arranged in the middle area of the housing; the heat transfer plate is fixedly arranged in the cavity formed between the inner wall of the housing and the outer wall of the internal components; the internal components sequentially include a conical pressure increasing section, a cylindrical gradually expanding section, and a diversion cone from top to bottom; the air outlet of the diversion cone is fixedly connected to the air inlet of the cylindrical gradually expanding section; the air outlet of the cylindrical gradually expanding section is fixedly connected to the air inlet of the conical pressure increasing section; diversion air inlets are provided on the conical pressure increasing section and the cylindrical gradually expanding section.

[0006] As a preferred solution, the diversion cone of the present invention includes a conical gradually shrinking section and a cylindrical stable section; the upper end of the cylindrical stable section is fixedly connected to the lower end of the conical gradually shrinking section.

[0007] Further, when the ratio of the internal pressure to the external pressure of the housing is 1.4 in the present invention, the ratio of the cross-sectional area of the end of the air outlet of the conical pressure increasing section to the cross-sectional area of the end of the air outlet of the diversion cone is 1.27.

[0008] Furthermore, the ratios of the lengths of the cylindrical stabilizing section, conical tapering section, cylindrical expanding section, and conical diffusing section of the present invention to the diameter of the outlet port of the conical diffusing section are 0.5, 0.9, 6.0, and 6.9 respectively.

[0009] The present invention can continuously accelerate the discharge of the pyrolysis products generated by the pyrolysis of oil shale in the internal components. The pyrolysis products in the reactor will also continuously flow towards the internal components. The heat carried during the gas flow process will be transferred to the inner-layer oil shale, accelerating the pyrolysis of the inner-layer oil shale, avoiding the large accumulation of volatile gases in the reactor and the secondary cracking due to high-temperature heating, and being beneficial to improving the pyrolysis rate and tar yield. By using the internal component reactor of the present invention, the evaporation-condensation rate of water in the central oil shale of the bed layer can be increased, and the heating rate can be increased. When the furnace temperature is relatively high, the setting of the internal components can more effectively improve the tar yield. The addition of the internal components makes the gaseous tar flow from the "high-temperature zone" at the time of generation to the "low-temperature zone" in the center of the bed layer, avoiding the high-temperature cracking of tar and improving the tar yield of the externally heated oil shale pyrolysis reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be further described below in conjunction with the drawings and specific embodiments. The usage method and scope of the present invention are not limited only to the expressions of the following content.

[0011] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0012] In the figure: 1, outer shell; 2, heat transfer plate; 3, internal component; 301, conical diffusing section; 302, cylindrical expanding section; 303, flow guiding cone; 304, flow guiding air inlet; 4, conical tapering section; 5, cylindrical stabilizing section; 6, oil shale. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] See Figure 1 As shown, the externally heated fixed-bed oil shale pyrolysis reactor includes an outer shell 1, a heat transfer plate 2, and an internal component 3; the internal component 3 is vertically and fixedly arranged in the middle area of the outer shell 1; the heat transfer plate 2 is fixedly arranged in the cavity formed between the inner wall of the outer shell 1 and the outer wall of the internal component 3; the internal component 3 successively includes a conical diffusing section 301, a cylindrical expanding section 302, and a flow guiding cone 303 from top to bottom; the outlet of the flow guiding cone 303 is fixedly connected to the inlet of the cylindrical expanding section 302; the outlet of the cylindrical expanding section 302 is fixedly connected to the inlet of the conical diffusing section 301; a flow guiding air inlet 304 is arranged on the conical diffusing section 301 and the cylindrical expanding section 302.

[0014] The flow guiding cone 303 of the present invention includes a conical tapering section 4 and a cylindrical stabilizing section 5; the upper end of the cylindrical stabilizing section 5 is fixedly connected to the lower end of the conical tapering section 4.

[0015] When the ratio of the internal pressure to the external pressure inside the housing 1 in the present invention is 1.4, the ratio of the cross-sectional area of the outlet end of the conical diffuser section 301 to the cross-sectional area of the outlet end of the flow guiding cone 303 is 1.27.

[0016] For the present invention, the ratios of the lengths of the cylindrical stabilizing section 5, the conical tapering section 4, the cylindrical expanding section 302 and the conical diffuser section 301 to the diameter of the outlet port of the conical diffuser section 301 are 0.5, 0.9, 6.0 and 6.9 respectively.

[0017] The internal component of the present invention adopts the internal component of a conical-flow guiding type supersonic nozzle. By adjusting the position of the flow guiding cone, the throat area of the supersonic nozzle can be adjusted. The cylindrical expanding section 302 adopts a circular cross-section. Compared with the cross-section of an annular nozzle, it has a small pressure loss and is used to guide and accelerate the pyrolysis products of oil shale to discharge from the reactor, and can generate a huge thrust, acting as a flow velocity increaser. For the structural design of the internal component, first, the throat size of the outlet port of the conical diffuser section 301 is determined according to the pressure ratio of the outlet of the fixed-bed oil shale pyrolysis reactor and the internal gas, and then the area ratio corresponding to the designed Mach number is determined according to the one-dimensional isentropic tube flow theory in aerodynamics, and the ratios of the lengths of different functional sections to the inlet diameter are optimized. According to the analysis, when the ratio of the internal pressure to the external pressure inside the housing 1 is 1.4, the ratio of the cross-sectional area of the outlet end of the conical diffuser section 301 to the cross-sectional area of the outlet end of the flow guiding cone 303 is 1.27.

[0018] The internal component of the present invention realizes the adjustable throat area of the supersonic nozzle by adjusting the position of the flow guide cone 303. The expansion section adopts a circular cross-section, and compared with the cross-section of the annular nozzle, the pressure loss is small. When the externally heated fixed-bed oil shale pyrolysis reactor is working, heating is carried out in the furnace body, and heat will be transferred to the oil shale 6 through the heat transfer plate 2. When the oil shale 6 is subjected to high temperature, pyrolysis occurs, and the pyrolysis products will enter the interior through some flow guide air inlets 304 on the surface of the internal component. The internal component will guide and accelerate the pyrolysis products. The guiding can make the air flow near the outer side of the reactor carry heat to the inside of the reactor and transfer it to the low-temperature oil shale, reduce the temperature difference between the inner and outer oil shales, accelerate the pyrolysis of the low-temperature oil shale inside, and reduce the secondary pyrolysis of the high-temperature oil shale outside; the acceleration can make the pyrolysis products be discharged from the reactor faster, preventing gas accumulation and secondary pyrolysis. The principle is that the pyrolysis products move in the internal component following the principle that the flow velocity is large at the small cross-section and small at the large cross-section when the fluid moves in the pipe. Therefore, the air flow is continuously accelerated, and when it reaches the narrow throat, the flow velocity has exceeded the speed of sound. However, the transonic fluid no longer follows the principle that the flow velocity is large at the small cross-section and small at the large cross-section during movement, but on the contrary, the larger the cross-section, the faster the flow velocity. So in the stage after the throat of the outlet port of the conical diffuser section 301, the flow velocity of the volatile gas air flow is further accelerated, thus generating a huge thrust. This internal component is a typical energy conversion device. During the internal flow process of the gas, the enthalpy energy is converted into kinetic energy, and finally a supersonic air flow is obtained, thereby improving the efficiency and reducing the pressure energy loss, playing the role of a flow velocity increaser. An important influencing factor in the design of the internal component is the nozzle area ratio. The nozzle area ratio is defined as the ratio of the cross-sectional area of the outlet end of the conical diffuser section 301 to the cross-sectional area of the outlet end of the flow guide cone 303. It is the core structural parameter of the device and has an extremely important influence on the internal flow field of the nozzle. Therefore, the structure of the internal component must be reasonably designed and optimized to ensure that a supersonic flow state is achieved and maintained in the expansion section of the internal component. For the structural design of the internal component, first, the throat size is determined according to the flow rate provided by the laboratory, and then the area ratio corresponding to the designed Mach number is determined according to the one-dimensional isentropic tube flow theory in aerodynamics, and optimized design is carried out for different area ratios. According to the analysis, when the ratio of the internal pressure to the external pressure in the outer shell 1 is 1.4, the ratio of the cross-sectional area of the outlet end of the conical diffuser section 301 to the cross-sectional area of the outlet end of the flow guide cone 303 is 1.27.

[0019] Compared with the existing technologies, the present invention has the following beneficial effects: When using a traditional gas collecting pipe, the porosity of the oil shale layer increases due to the evaporation of water and the release of volatile components. The pyrolysis degree near the high-temperature wall surface is deeper, resulting in a larger porosity than that in the central region of the bed and a lower pressure. The porosity in the fixed-bed internal pyrolysis reactor is non-uniform along the radial position. At the same heating time, the porosity of the oil shale layer near the wall is larger, and the porosity of the oil shale layer in the center of the bed is the smallest. The non-uniform distribution of the porosity in the reactor will affect the flow behavior of the generated volatile gas. Since the porosity near the heating wall surface is relatively higher, the pressure drop of the bed near the heating wall surface is lower, causing the volatile products generated inside the bed to tend to pass through the high-temperature wall surface region before flowing out of the reactor. The tar product generated by pyrolysis will undergo secondary cracking at high temperatures, and the secondary cracking of tar will directly affect the final yield of tar. In the traditional gas collecting pipe reactor, the flow of the generated volatile gas from the "low-temperature zone" to the "high-temperature zone" is slower than that of the new internal component for discharging the volatile components, resulting in gas accumulation. Therefore, by adopting the internal component of the present invention, the evaporation process of the internal moisture of the oil shale can be significantly accelerated, and the evaporation position of the moisture gradually moves towards the center of the bed. The water evaporation-condensation rate of the oil shale in the center of the bed increases, and the heating rate increases, which are attributed to the flow of the gas generated near the side wall towards the center of the bed. When the temperature of the reactor is relatively high, the setting of the internal component can more effectively increase the tar yield, causing the gaseous tar to flow from the "high-temperature zone" at the time of generation to the "low-temperature zone" in the center of the bed, avoiding the high-temperature cracking of tar and improving the tar yield of the externally heated oil shale pyrolysis reactor.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0021] In the present invention, unless otherwise clearly defined and limited, terms such as "set", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An externally heated fixed-bed oil shale pyrolysis reactor, characterized in that, It includes a housing (1), a heat transfer plate (2) and an internal component (3); the internal component (3) is vertically and fixedly arranged in the middle area of the housing (1); the heat transfer plate (2) is fixedly arranged in the cavity formed by the inner wall of the housing (1) and the outer wall of the internal component (3); the internal component (3) successively includes a conical diffuser section (301), a cylindrical gradually expanding section (302) and a flow guide cone (303) from top to bottom; the air outlet of the flow guide cone (303) is fixedly connected to the air inlet of the cylindrical gradually expanding section (302); the air outlet of the cylindrical gradually expanding section (302) is fixedly connected to the air inlet of the conical diffuser section (301); a plurality of flow guide air inlets (304) are arranged on both the conical diffuser section (301) and the cylindrical gradually expanding section (302); the flow guide cone (303) includes a conical gradually shrinking section (4) and a cylindrical stable section (5); the upper end of the cylindrical stable section (5) is fixedly connected to the lower end of the conical gradually shrinking section (4); when the ratio of the internal pressure to the external pressure in the housing (1) is 1.4, the ratio of the cross-sectional area of the air outlet end of the conical diffuser section (301) to the cross-sectional area of the air outlet end of the flow guide cone (303) is 1.27; the ratios of the lengths of the cylindrical stable section (5), the conical gradually shrinking section (4), the cylindrical gradually expanding section (302) and the conical diffuser section (301) to the diameter of the air outlet port of the conical diffuser section (301) are 0.5, 0.9, 6.0 and 6.9 respectively.

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