Device for preparing sebacic acid by cracking ricinoleic acid

Abstract

The invention belongs to the technical field of chemical production, and particularly relates to a device for preparing sebacic acid by cracking ricinoleic acid, which comprises a barrel, an elliptical head is arranged at the top of the barrel, an exhaust port and a feed port are arranged on the elliptical head, a flat-bottom head is arranged at the bottom of the barrel, a discharge port is arranged on the flat-bottom head, and the discharge port is connected with a spiral discharge device; a stirrer is arranged inside the barrel, a spiral jacket is arranged on the outer wall of the barrel, a heat-conducting oil inlet and a heat-conducting oil outlet are formed in the spiral jacket, the heat-conducting oil inlet is formed in the lower part of the spiral jacket, and the heat-conducting oil outlet is formed in the upper part of the spiral jacket; the stirrer is of a combined structure and comprises a middle shaft and a cross-shaped outer frame, and the cross-shaped outer frame comprises main blades, an upper connecting strip and a lower connecting strip. The device can provide a good mixing effect in the radial direction, strengthen the heat transfer capability, reduce material backmixing in the axial direction, meet the requirement of reaction temperature, improve the production efficiency of ricinoleic acid cracking and improve the yield.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical production, and particularly relates to a device for preparing sebacic acid by cleaving castor oil acid. BACKGROUND

[0002] Sebacic acid is an important fine chemical intermediate, which is mainly used for producing polyamide resin and sebacic acid ester compounds, and has a wide application in different fields such as engineering plastics, textiles, plasticizers, medical treatment and the like.

[0003] There are two main production processes for sebacic acid, namely, a biological castor oil cleavage method and an alkane biological fermentation method. The castor oil cleavage method uses castor oil as a raw material, meets the requirements of green and sustainable development, and has a good development prospect because the biological sebacic acid obtained by the route is a main raw material for biological long-chain polyamide.

[0004] The preparation of sebacic acid by the castor oil cleavage method uses castor oil as a starting raw material, and oxygen zinc as a catalyst. Under the conditions of temperature rise and pressure rise, a hydrolysis reaction occurs to generate castor oil acid and glycerol. Castor oil acid is obtained by separation, and phenolic substances are added as a diluent to perform a cleavage reaction with liquid alkali at 250-280 DEG C to generate sebacic acid disodium salt, secondary octanol and hydrogen. Finally, the product is prepared after neutralization, decolorization, crystallization and drying.

[0005] The production and preparation of sebacic acid are greatly affected by the cleavage process in terms of quality and color value. In the process of castor oil acid alkali cleavage, castor oil acid and alkali are respectively added from the top of the kettle. Once they enter the kettle and are rapidly dehydrated, on the one hand, a large amount of heat is taken away, which causes the temperature of the upper part of the cleavage kettle to drop, and on the other hand, the newly added materials in the kettle are not uniformly mixed, which seriously affects the heat and mass transfer and directly affects the quality and yield of the product.

[0006] The utility model patent CN211800768U proposes a castor oil acid cleavage device. The device is provided with stirring paddles, the stirring paddles are 3-5 layers of folding paddle type, 3-5 layers of paddles are arranged on the central shaft of the stirring paddles, each layer has 3 paddles, and the paddles of each layer are arranged in a staggered 120° arrangement. A double-loop heat carrier structure is connected to the cylinder of the cleavage device, which can control the temperature of the upper and lower parts of the cylinder, ensure that the temperature of the cylinder is 210-280 DEG C, solve the problem that the by-product sodium sebacate and ketone substances increase when the temperature of the traditional cleavage kettle is lower than 210 DEG C, and ensure that the temperature of the lower half of the cylinder is lower than 350 DEG C in the cleavage process to prevent the formation of paste and the like. Since the reaction system is a semi-solid material, the folding paddle type stirrer has limited mixing efficiency, and cannot solve the problem of material back mixing in the reactor; only the temperature of the upper part of the reactor can be controlled to be higher than 210 DEG C (the appropriate upper temperature is 250-260 DEG C).

[0007] Invention patent CN117258694A discloses an apparatus for producing sebacic acid from castor oil acid through cracking. Sodium hydroxide solution is injected into the inner cavity of a rotating tube through a feed pipe. The sodium hydroxide solution from the feed pipe is then forced into the inner cavity of the stirring shaft and the inner cavity of the reactor. The discharge port ensures sufficient contact between the raw material and the material in the reactor cavity, allowing for faster mixing. This avoids the situation where sodium hydroxide solution fed from the top dehydrates instantly upon entering the reactor, forming a solid and carrying away a large amount of heat, thus lowering the temperature in the upper part of the reactor cavity. This improves mixing efficiency to some extent. Simultaneously, a spring-loaded striking device vibrates the reactor, causing the material in the reactor and maturation chamber to vibrate, preventing material from adhering to the inner walls of the reactor and maturation chamber, and dislodging air bubbles. While this invention avoids rapid evaporation of water in the alkali solution and improves mixing efficiency, it fails to solve the problem of backmixing, resulting in large differences in material residence time and no axial temperature gradient. Furthermore, the apparatus has a complex mechanical structure, requiring significant maintenance for normal operation.

[0008] Utility model patent CN222401435U discloses a device for the pyrolysis of castor oil acid to produce sebacic acid. This device consists of two layers, separated by a partition plate. The partition plate has multiple gas dispersion channels made of a non-stick, high-temperature resistant material. These channels are angled, with the inlet and outlet symmetrically positioned to prevent the mixed liquid from splashing into the gas dispersion channels during stirring, thus avoiding interference with normal gas output. However, this invention only addresses the problem of material clogging the exhaust port during the pyrolysis reaction; it fails to improve the mixing efficiency, overcome backmixing, or address the axial gradient distribution within the reactor. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an apparatus for the pyrolysis of ricinoleic acid to prepare sebacic acid. The pyrolysis apparatus of this invention has a simple structure, provides good mixing for semi-solid materials, and achieves high pyrolysis conversion and yield.

[0010] To achieve the above technical objectives, the present invention provides the following technical solution: An apparatus for preparing sebacic acid by cracking ricinoleic acid includes a cylindrical body, the top of which has an elliptical end cap, an exhaust port and a feed port provided on the elliptical end cap, and the bottom of which has a flat-bottom end cap, a discharge port provided on the flat-bottom end cap, the discharge port being connected to a spiral discharge device. The cylinder is equipped with an agitator inside and a spiral jacket on its outer wall. The spiral jacket has a heat transfer oil inlet and a heat transfer oil outlet. The heat transfer oil inlet is located at the lower part of the spiral jacket, and the heat transfer oil outlet is located at the upper part of the spiral jacket. The agitator is a modular structure, comprising a central shaft and a cross-shaped outer frame. The cross-shaped outer frame includes a main impeller, an upper connecting strip, and a lower connecting strip. The lower end of the main impeller is connected to the central shaft via the lower connecting strip, and the upper-middle end of the main impeller is connected to the central shaft via the upper connecting strip. The width of the main impeller is 80-100mm. A suitable impeller width produces a good radial pushing effect during rotation. Furthermore, the cylinder is also equipped with a gas phase thermometer port, an upper thermometer port, and a lower thermometer port. The upper and lower thermometer ports are used to monitor the reaction temperature.

[0011] Furthermore, the cross-section of the central axis is shaped like a plum blossom; The main blade width is 80-100mm. A suitable blade width produces a better radial pushing effect during rotation; the length of the main blade is 85%-90% of the cylinder height. Furthermore, the upper connecting strip is positioned at 2 / 3 to 3 / 4 of the cylinder height, and the distance between the lower connecting strip and the bottom of the cylinder is 5-15 mm. The upper connecting strip is completely submerged in the material to prevent material from sticking.

[0012] Furthermore, each of the upper connecting strips is equipped with two equally spaced, vertically arranged auxiliary mixing blades. The width of the auxiliary mixing blades is 20-30mm, and their upper ends are flush with the upper ends of the main blades. The function of the auxiliary mixing blades is to perform preliminary mixing on the incoming materials.

[0013] Furthermore, the angle α between the main blade and the upper and lower connecting strips is 30-60°. A suitable angle produces a better radial pushing effect during rotation. The distance H between the outer edge of the main blade and the inner wall of the cylinder is no greater than 5mm.

[0014] Furthermore, the upper connecting strip is positioned below the liquid level of the material inside the cylinder, with the liquid level of the material being 75%-80% of the cylinder height. The upper connecting strip is positioned below the liquid level to prevent material from accumulating on the connecting strip.

[0015] Furthermore, the distance between the upper thermometer port and the upper connecting strip is 100-200mm, and the depth to which the upper thermometer port is inserted into the cylinder is 50-60mm; The distance between the lower thermometer port and the bottom of the cylinder is 200-300mm, and the depth to which the lower thermometer port is inserted into the cylinder is 50-60mm.

[0016] Furthermore, the feed inlet is provided with a combined feed pipe, which consists of an inner pipe and an outer pipe. The outer pipe is a castor oil acid feed pipe, and the inner pipe is a sodium hydroxide solution feed pipe.

[0017] Furthermore, the inner diameter of the cylinder is 400 mm, and the length-to-diameter ratio is 2.5-3.5. A reasonable length-to-diameter ratio is necessary to ensure complete reaction. If the length-to-diameter ratio is <2.5, the material residence time is too short and the reaction is incomplete; if the length-to-diameter ratio is >3.5, excessive evaporation of moisture can easily lead to reaction deterioration.

[0018] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are: (1) The present invention adopts a wall-mounted combined agitator, that is, it uses a cross-shaped inclined plate quasi-frame structure + plum blossom-shaped central shaft agitator to change the flow pattern of semi-solid material, so that the reactants can be fully mixed in the radial plane, and the temperature and concentration are basically consistent; specifically, during the operation of the agitator, the material in the wall direction can be pushed to the central shaft direction. After the material encounters the plum blossom-shaped central shaft, it will be pushed back to the wall direction. This is repeated continuously, and the material between the wall and the central shaft can be continuously mixed, and the heat transfer rate and mixing efficiency can be greatly improved.

[0019] (2) The combined stirrer attached to the wall of the present invention can continuously refresh the material in contact with the wall, which enhances the heat conduction capacity; and because heat transfer oil is used for heating, the heating temperature is much lower than that of molten salt, so even if the time is long, there will be no overheating phenomenon, reducing the generation of by-products.

[0020] (3) When using the pyrolysis device of the present invention, the material flows from top to bottom in the cylinder in a quasi-horizontal plug flow motion, which reduces the back mixing of materials between different temperatures and concentrations. The material temperature gradually rises, which meets the gradient requirement of the pyrolysis reaction temperature from low to high. The material residence time distribution is narrower (i.e., first in first out, last in last out), thereby achieving precise control of the reaction process.

[0021] (4) Existing pyrolysis reactors generally use molten salt as the heat transfer medium, which has a low heat transfer coefficient. In addition, the reactants are semi-solid and have a small specific heat transfer area, so the heat transfer effect is not good. The pyrolysis device of the present invention has a small inner diameter, small volume, and large specific heat transfer area. At the same time, it uses heat transfer oil with a relatively high heat transfer coefficient as the heat transfer medium and uses a spiral jacket structure to avoid the circulation taking a shortcut, which greatly improves the heat transfer efficiency and effectively reduces the occurrence of side reactions.

[0022] (5) The top of the pyrolysis reaction device of the present invention has sufficient gas phase space, which can reduce gas entrainment, facilitate the settling and separation of gas and liquid materials, and avoid material blockage of gas phase outlet.

[0023] (6) Existing pyrolysis processes usually use phenolic substances as diluents, which improves the heat and mass transfer effect to a certain extent. However, when using the pyrolysis device of the present invention to produce sebacic acid, less or no phenolic substances can be added, and good mixing effect, temperature gradient and high product yield can still be obtained, while reducing the generation of pollutants from the source. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the apparatus for preparing sebacic acid by cracking ricinoleic acid in an embodiment of the present invention.

[0025] Figure 2 yes Figure 1 A schematic diagram of the combined stirrer in the device.

[0026] Figure 3 yes Figure 1 A schematic diagram of the radial plane material flow in the device.

[0027] Figure 4 yes Figure 1 A schematic diagram of the plum blossom-shaped central axis in the device.

[0028] Figure 5 yes Figure 1 A schematic diagram of the cross-shaped outer frame in the device.

[0029] Figure 6 This is a gas chromatogram of the pyrolyzed sample in the example.

[0030] Explanation of reference numerals in the attached drawings: 1-Castor oleic acid feed pipe; 2-Sodium hydroxide aqueous solution feed pipe; 3-Heat transfer oil outlet; 4-Upper connecting bar; 5-Cylinder body; 6-Spiral jacket; 7-Lower connecting bar; 8-Heat transfer oil inlet; 9-Spiral discharge device; 10-Exhaust port; 11-Gas phase thermometer port; 12-Auxiliary mixing blade; 13-Upper thermometer port; 14-Central shaft; 15-Main blade; 16-Lower thermometer port. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] like Figure 1 As shown, an apparatus for preparing sebacic acid by cracking ricinoleic acid includes a cylindrical body 5, which is cylindrical with an inner diameter of 400 mm and a length of 1200 mm.

[0033] The top of the cylinder 5 has an elliptical end cap, on which an exhaust port 10 (DN50, representing a nominal diameter of 32 mm) and a feed port are provided. The bottom of the cylinder 5 has a flat-bottom end cap, on which a discharge port (DN65) is provided. The discharge port is connected to a spiral discharge device 9. The feed inlet is equipped with a combined feed pipe, which consists of an inner pipe and an outer pipe. The outer pipe is a castor oil acid feed pipe 1 (DN40), and the inner pipe is a sodium hydroxide solution feed pipe 2 (DN25).

[0034] An agitator is installed inside the cylinder 5, and a spiral jacket 6 is installed on the outer wall of the cylinder 5. A heat transfer oil inlet 8 (DN25) and a heat transfer oil outlet 3 (DN32) are installed on the spiral jacket 6. The heat transfer oil inlet 8 is located at the lower part of the spiral jacket 6, and the heat transfer oil outlet 3 is located at the upper part of the spiral jacket 6. The cylinder 5 is also equipped with a gas phase thermometer port 11, an upper thermometer port 13 and a lower thermometer port 16. The upper thermometer port 13 and the lower thermometer port 16 are used to monitor the reaction temperature.

[0035] The gas phase thermometer port 11 is located at the straight edge of the elliptical head, the lower thermometer port 16 is located at a height of 250mm in the cylinder 5, and the upper thermometer port 13 is located at a height of 800mm in the cylinder 5.

[0036] like Figure 2 As shown, the stirrer is a modular structure, including a central shaft 14 and a cross-shaped outer frame. The central shaft 14 is 1020mm long, and its cross-section is quincunx-shaped. The circumscribed circle diameter of the central shaft 14 is 200mm, and the inscribed circle diameter is 141mm. Its cross-section is shown in the figure. Figure 4 As shown.

[0037] The cross-shaped outer frame includes four main blades 15, an upper connecting strip 4, and a lower connecting strip 7. The lower end of each main blade 15 is connected to the central shaft 14 via the lower connecting strip 7, and the upper middle end of each main blade 15 is connected to the central shaft 14 via the upper connecting strip 4. The main blade 15 has a width L = 80mm and a length of 1020mm, and its cross-section is as follows. Figure 5 As shown. The four upper connecting strips 4 and the four lower connecting strips 7 all form a cross shape.

[0038] The upper connecting strip 4 is installed at a height of 900mm, and the distance between the lower connecting strip 7 and the bottom of the cylinder 5 is 15mm.

[0039] Each upper connecting bar 4 is equipped with two equally spaced, vertically arranged auxiliary mixing blades 12. The width of the auxiliary mixing blades 12 is 25mm and the length is 90mm. Their upper ends are flush with the upper ends of the main blades 15.

[0040] like Figure 5 As shown, the angle α between the main blade 15 and the upper connecting strip 4 and the lower connecting strip 7 is 30°, and the distance H between the outer edge of the main blade 15 and the inner wall of the cylinder 5 is 4mm.

[0041] The upper connecting strip 4 is positioned below the liquid level of the material inside the cylinder 5, and the liquid level of the material is 75%-80% of the height of the cylinder 5.

[0042] The upper thermometer port 13 is inserted into the cylinder 5 to a depth of 50-60 mm, and the lower thermometer port 16 is inserted into the cylinder 5 to a depth of 50-60 mm. The specific insertion depth can be 50 mm, 55 mm, 60 mm, etc.

[0043] During production, preheated ricinoleic acid enters the cylinder 5 at a flow rate of 300 kg / h through the ricinoleic acid feed pipe 1. A 45-50% sodium hydroxide aqueous solution flows into the cylinder 5 at a flow rate of 350 kg / h through the sodium hydroxide solution feed pipe 2. Hydrogen and 2-octanol are discharged from the exhaust port 10. High-temperature heat transfer oil at 300°C enters the spiral jacket 6 through the heat transfer oil inlet 8 and flows out through the heat transfer oil outlet 3. The central shaft 14 drives the main impeller 15 and the auxiliary mixing impeller 12 to rotate synchronously at a speed of 30 rpm, causing the ricinoleic acid and sodium hydroxide solution to mix and flow radially. Figure 3 As shown, in the radial plane, the main blade 15 pushes the material adhering to the wall towards the central shaft 14. After encountering the central shaft 14, the material is pushed back towards the wall. In this way, the material between the inner wall of the cylinder 5 and the central shaft 14 can be continuously mixed. The material in contact with the wall can also be continuously renewed, avoiding the material adhering to the wall for a long time, which would lead to overheating and an increase in by-products. At the same time, it also improves the heat transfer effect. More importantly, in the axial direction, the material moves downward in a similar plug flow pattern, reducing back mixing. The material temperature gradually rises from 240-250℃ at the top, reaching 280-290℃ at the outlet, forming a good temperature gradient distribution. Finally, it enters the screw discharge device 9 from the discharge port and is discharged.

[0044] 1. Take 10g of pyrolysis sample, add 50mL of water to dissolve, add 20% sulfuric acid to adjust the pH to pH=5.8-6.2, separate and remove the upper oil phase, continue to adjust the pH of the lower aqueous phase to 2.0-3.0, boil and cool to room temperature, filter, wash with water until neutral, dry and set aside.

[0045] 2. Weigh 0.25g, 0.50g, 0.75g, 1.0g, and 1.25g of sebacic acid standard and 0.75g of the above sample into different 10mL volumetric flasks, respectively, and add 25% tetramethylammonium hydroxide to adjust the pH value to pH=9.0, and then make up to volume.

[0046] 3. Inject the above standard sample solution and the sample solution to be tested into the gas chromatograph, perform gas chromatographic analysis according to the above chromatographic conditions, and record the chromatogram.

[0047] 4. Determine the content using the external standard method based on the chromatogram.

[0048] Detection spectrum attached Figure 1 Zhang (using the reactor of this invention, with a mass ratio of alkali solution: ricinoleic acid = 1.1:1, reaction temperature 280-290℃, reaction time 35 min) test results, see [link to test results]. Figure 6 As shown, from Figure 6 The analysis results show that the crude sebacic acid has high purity and very few byproducts.

[0049] This invention addresses the semi-solid nature of pyrolysis materials by designing a quasi-horizontal plug flow reactor. In this reactor, the material moves in a manner similar to a piston flow along the reactor axis. This effectively overcomes the disruption of reactant concentration gradients caused by material backmixing in traditional pyrolysis reactors, resulting in a narrower material residence time distribution (i.e., first-in-first-out, last-in-last-out), thereby enabling precise control of the reaction process.

[0050] Based on the characteristics of the reactor and the requirements of the castor oil pyrolysis process, a matching agitator (mainly referring to the structure of the agitator) was designed to achieve efficient mass and heat transfer of materials in the reaction. On the one hand, the castor oil acid and the alkaline solution are mixed rapidly to ensure that the temperature and concentration of the materials in the radial plane are basically consistent. On the other hand, the axial temperature is distributed in a progressive manner (from low to high), thereby avoiding problems such as local overheating, excessive evaporation of water leading to deterioration of mass transfer, or incomplete reaction due to short residence time. This provides suitable process conditions for the efficient pyrolysis of castor oil acid.

[0051] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An apparatus for preparing sebacic acid by pyrolysis of ricinoleic acid, characterized in that, Includes a cylinder (5), the top of the cylinder (5) has an elliptical end cap, the elliptical end cap is provided with an exhaust port (10) and a feed port, the bottom of the cylinder (5) has a flat end cap, the flat end cap is provided with a discharge port, the discharge port is connected to a spiral discharge device (9). The cylinder (5) is equipped with a stirrer inside and a spiral jacket (6) is provided on the outer wall of the cylinder (5). The spiral jacket (6) is provided with a heat transfer oil inlet (8) and a heat transfer oil outlet (3). The heat transfer oil inlet (8) is located at the lower part of the spiral jacket (6) and the heat transfer oil outlet (3) is located at the upper part of the spiral jacket (6). The stirrer is a combined structure, including a central shaft (14) and a cross-shaped outer frame. The cross-shaped outer frame includes a main blade (15), an upper connecting strip (4) and a lower connecting strip (7). The lower end of the main blade (15) is connected to the central shaft (14) through the lower connecting strip (7), and the upper middle end of the main blade (15) is connected to the central shaft (14) through the upper connecting strip (4).

2. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, The cylinder (5) is also provided with a gas phase thermometer port (11), an upper thermometer port (13) and a lower thermometer port (16), which are used to monitor the reaction temperature.

3. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, The cross-section of the central axis (14) is plum blossom shaped; The width of the main blade (15) is 80-100mm, and the length of the main blade (15) is 85%-90% of the height of the cylinder (5).

4. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, The upper connecting strip (4) is located at 2 / 3-3 / 4 of the height of the cylinder (5), and the distance between the lower connecting strip (7) and the bottom of the cylinder (5) is 5-15mm.

5. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, Each of the upper connecting strips (4) is equipped with two vertically arranged auxiliary mixing blades (12) at equal intervals. The width of the auxiliary mixing blades (12) is 20-30mm, and their upper ends are flush with the upper ends of the main blades (15).

6. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, The angle α between the main blade (15) and the upper connecting strip (4) and the lower connecting strip (7) is 30-60°, and the distance H between the outer edge of the main blade (15) and the inner wall of the cylinder (5) is not greater than 5mm.

7. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, The upper connecting strip (4) is positioned below the liquid level of the material inside the cylinder (5), and the liquid level of the material is 75%-80% of the height of the cylinder (5).

8. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 2, characterized in that, The distance between the upper thermometer port (13) and the upper connecting strip (4) is 100-200mm, and the depth of the upper thermometer port (13) inserted into the cylinder (5) is 50-60mm. The distance between the lower thermometer port (16) and the bottom of the cylinder (5) is 200-300mm, and the depth to which the lower thermometer port (16) is inserted into the cylinder (5) is 50-60mm.

9. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, The feed inlet is equipped with a combined feed pipe, which consists of an inner pipe and an outer pipe. The outer pipe is a castor oil acid feed pipe (1), and the inner pipe is a sodium hydroxide solution feed pipe (2).

10. The apparatus for preparing sebacic acid by pyrolysis of castor oil acid according to claim 1, characterized in that, The inner diameter of the cylinder (5) is 400 mm and the length-to-diameter ratio is 2.5-3.5.

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