Equipment for manufacturing fatty acid methyl esters and method for manufacturing fatty acid methyl esters

Abstract

To provide a manufacturing facility that can be implemented on an industrial scale and continuously produce fatty acid methyl esters with a low acid value, and to provide a method for producing fatty acid methyl esters using such a manufacturing facility. [Solution] A fatty acid methyl ester production facility comprising a first raw material tank for containing fatty acids, a second raw material tank for containing methanol, a reaction tower with a first raw material supply line connected to the first raw material tank at the top and a second raw material supply line connected to the second raw material tank at the bottom, and a removal line for removing the product from the reaction tower. The reaction tower is a bubble tower with 49 reaction stages. A first heat exchanger is provided for heat exchange between the first raw material supply line and the removal line.

Description

Technical Field

[0001] The present invention relates to a production facility for fatty acid methyl ester and a method for producing fatty acid methyl ester.

Background Art

[0002] When industrially producing an ester compound, it is known to use a bubble-cap column as a distillation column for distillation purification of a reaction product. For example, Patent Document 1 discloses a method for producing a carboxylic acid ester, which includes a step A of reacting an aliphatic carboxylic acid and an aliphatic alcohol in a reactor, a step B of supplying the reaction solution obtained in step A to a distillation column, distilling off the carboxylic acid ester produced from the top of the column and the by-produced water, and recovering the unreacted aliphatic carboxylic acid from the bottom of the column, and a step C of recycling the unreacted aliphatic carboxylic acid recovered in step B to step A, and discloses using a bubble-cap column in step B.

[0003] Patent Document 2 is an invention characterized by using a specific catalyst in the production of malonic acid diester, and discloses that the transesterification of dimethyl malonate is continuously carried out using a bubble-cap column. Examples in Patent Document 2 disclose an example in which dimethyl malonate and a transesterification catalyst are supplied from the top of a bubble-cap column, and ethanol is supplied from near the bottom of the column for transesterification.

[0004] On the other hand, Patent Document 3 discloses a form of a plate column equipped with bubble caps. Patent Document 3 discloses a plate column including a tray and a perforated plate provided on the tray, and a gas blocking portion for blocking the flow of gas is provided near the weir side of the perforated plate. The plate column of Patent Document 3 discloses that the flow of gas in the tray is controlled by the gas blocking portion, the pressure loss is reduced, and the gas-liquid stirring efficiency is improved.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-241765 [Patent Document 2] Japanese Patent Publication No. 2001-233823 [Patent Document 3] Patent No. 5429083 [Overview of the project] [Problems that the invention aims to solve]

[0006] As described above, it is known that foam towers are used in the conventional production of ester compounds, and the form of tray towers has also been investigated. However, there is no concrete knowledge of equipment suitable for the production of fatty acid methyl esters using dehydration reactions, and the need for equipment that can produce fatty acid methyl esters continuously and efficiently continues. In view of this situation, the present invention aims to provide a production facility that can be implemented on an industrial scale and can continuously produce fatty acid methyl esters with a low acid value, and to provide a method for producing fatty acid methyl esters using such a production facility. [Means for solving the problem]

[0007] The fatty acid methyl ester production apparatus according to this disclosure comprises a first raw material tank for containing fatty acids, a second raw material tank for containing methanol, a reaction tower with a first raw material supply line connected to the first raw material tank at the top and a second raw material supply line connected to the second raw material tank at the bottom, and a removal line for removing the product from the reaction tower. The reaction tower is a bubble tower having 40 to 55 reaction stages and is equipped with a first heat exchanger for heat exchange between the first raw material supply line and the removal line.

[0008] According to the aforementioned manufacturing equipment, the fatty acid supplied from the top of the reaction tower and the methanol supplied from the bottom of the reaction tower are thoroughly mixed in the reaction tower, allowing for the stable production of fatty acid methyl esters with a low acid value. Furthermore, in the first heat exchanger, the heat contained in the reaction product (fatty acid methyl ester) discharged from the reaction tower is used to heat the raw material fatty acid. This configuration improves energy utilization efficiency and reduces energy consumption, resulting in a manufacturing facility with reduced energy consumption.

[0009] In the fatty acid methyl ester production apparatus, the bubble tower is preferably constructed by stacking reaction stages vertically, each having a height of 30-45 cm and a diameter of 50-70 cm. The bubble tower comprises a first cylinder rising from the bottom surface of the reaction stage, a second cylinder rising from the bottom surface of the reaction stage and being shorter in height than the first cylinder, and a third cylinder positioned inside the first cylinder, penetrating the bottom surface of the reaction stage and having a portion that protrudes upward from the bottom surface and a portion that protrudes downward from the bottom surface. The third cylinder is preferably installed so as to be inserted into the second cylinder of the reaction stage one level below. The third cylinder is a downcomer, and by configuring the downcomer in this form, splashing of liquid flowing down from the upper reaction stage can be prevented, and gas-liquid mixing can be reliably carried out in the subsequent reaction stage. Specifically, if the reaction stage is 40 cm high and 60 cm in diameter, the first cylinder may be 38 cm high and 13 cm in diameter, and the second cylinder may be 30 cm high and 13 cm in diameter. In this case, the third cylinder may have a portion that protrudes 25 cm above the bottom surface and a portion that protrudes 37 cm below the bottom surface, with a total length of 62 cm.

[0010] In the fatty acid methyl ester production apparatus described above, it is preferable that each of the first cylinder and the second cylinder has a notched hole formed in the peripheral wall of the rising portion from the bottom surface of the reaction stage.

[0011] In the fatty acid methyl ester production apparatus described above, it is preferable that each of the reaction stages is equipped with 10 to 24 bubble bells.

[0012] The method for producing fatty acid methyl esters according to this disclosure is a method carried out in the fatty acid methyl ester production facility described above. The production method according to this disclosure includes an esterification step in which a fatty acid is introduced from the first raw material tank into the reaction tower and methanol is introduced from the second raw material tank into the reaction tower, and the fatty acid and methanol are brought into contact in the reaction tower. In the first heat exchanger, after the esterification step, heat exchange is performed between the reactant discharged from the reaction tower and flowing through the extraction line and the fatty acid discharged from the first raw material tank and flowing through the first raw material supply line.

[0013] In the above manufacturing method, it is preferable to include a step of adding iron powder to the fatty acid contained in the first raw material tank.

[0014] In the esterification step, it is preferable that the ratio of the amount of fatty acid charged to the reaction tower per unit time to the amount of methanol charged to the reaction tower is 1:1.8 to 1:3.0 (molar ratio). [Effects of the Invention]

[0015] The manufacturing equipment described herein provides a manufacturing facility that can be implemented on an industrial scale and continuously produce fatty acid methyl esters with a low acid value. Furthermore, a method for producing fatty acid methyl esters using such manufacturing equipment is also provided. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic diagram showing the configuration of the manufacturing equipment related to this disclosure. [Figure 2] Figure 2 is a schematic diagram showing the reaction tower of the manufacturing facility according to this disclosure. [Figure 3] Figure 3 is a schematic diagram showing the interior of the reaction tower of the manufacturing equipment according to this disclosure. [Figure 4] Figure 4 is a schematic diagram showing the interior of the reaction tower of the manufacturing equipment according to this disclosure. [Modes for carrying out the invention]

[0017] [Overview of Embodiment] Embodiments of a production facility and a production method for fatty acid methyl esters according to the present disclosure will be described. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less".

[0018] (Production Facility) FIG. 1 is a schematic diagram showing the configuration of a production facility for fatty acid methyl esters according to the present disclosure. Referring to FIG. 1, the production facility 1 is generally a facility in which a first raw material tank 11 for storing fatty acids and a second raw material tank 12 for storing methanol are each connected to a reaction tower 20 via pipes, and the fatty acid methyl ester produced by the reaction in the reaction tower 20 is taken out from the reaction tower 20 to a product tank 13.

[0019] A pipe 42 as a first raw material supply line connected to the first raw material tank 11 is connected to the upper part of the reaction tower 20. A pipe 52 as a second raw material supply line connected to the second raw material tank 12 is connected to the lower part of the reaction tower 20. A pipe 61 as a product extraction line for the product produced by the reaction in the reaction tower 20 is connected to the bottom of the reaction tower 20. Details of the reaction tower 20 will be described later.

[0020] A pipe 41 is connected to the first raw material tank 11 for storing fatty acids. The pipe 41 passes through a first heat exchanger 31 and a heater 32 and is connected to the pipe 42. The pipe 61 is connected to a pipe 62 via a pump 38 and the first heat exchanger 31. In the first heat exchanger 31, heat exchange occurs between the raw material (fatty acid) flowing through the pipe 41 and the product flowing through the pipe 61. In the first heat exchanger 31, the raw material flowing through the pipe 41 is heated up, and the temperature of the product flowing through the pipe 61 drops. The raw material heated in the first heat exchanger 31 is further heated in a heater 32 equipped with a heater to become a high-temperature (for example, 260°C) liquid fatty acid. The fatty acid, which is a high-temperature liquid, is supplied to the upper part of the reaction tower 20 through the pipe 42.

[0021] A pipe 51 is connected to a second raw material tank 12 containing methanol. The pipe 51 passes through an evaporator 33 and a heater 34, and then connects to a pipe 52. The methanol vapor vaporized in the evaporator 33 is further heated in the heater 34 to become high-temperature (e.g., 270°C) methanol gas. The high-temperature methanol gas is supplied to the bottom of the reaction tower 20 through the pipe 52.

[0022] High-temperature liquid fatty acids supplied from the top of the reaction tower 20 flow downward due to gravity. High-temperature gas methanol supplied from the bottom of the reaction tower 20 rises within the reaction tower 20. A dehydration reaction occurs when the flowing fatty acids and rising methanol come into contact, producing fatty acid methyl esters and water.

[0023] A reflux line, pipe 71, is connected to the top of the reaction column 20. Pipe 71 passes through the second heat exchanger 35 to the reflux drum 36. Pipe 72 connects to the reflux drum 36, and the mixture of reliquefied fatty acids, methanol, and water is refluxed back into the reaction column 20. Through pipe 73 connected to the reflux drum 36, a gas containing methanol and water is introduced into the distillation column 37. In the distillation column 37, methanol is separated by distillation. The methanol condensed in the distillation column 37 and the condenser 39 is supplied (recovered) through pipe 75 to the second raw material tank 12 containing methanol.

[0024] The piping 51 passes through a second heat exchanger 35 before reaching the evaporator 33. In the second heat exchanger 35, heat exchange occurs between the raw material (methanol) flowing through piping 51 and the evaporated mixture flowing through piping 71. In the second heat exchanger 35, the temperature of the raw material flowing through piping 51 rises, and the temperature of the evaporated mixture flowing through piping 71 decreases. The raw material heated in the second heat exchanger 35 is further heated and vaporized in the evaporator 33. By placing the second heat exchanger 35 before the evaporator 33, thermal energy in the manufacturing equipment can be used effectively.

[0025] Figure 2 is a schematic diagram showing the configuration of a reaction tower in a fatty acid methyl ester production facility according to this disclosure. The reaction tower 20 is a bubble tower with a large number of stages. The number of stages can be selected according to the target substance and preferred reaction conditions, and can be 40 to 55 stages. More specifically, with a reaction tower 20 consisting of 49 stages, fatty acid methyl esters can be produced efficiently, and fatty acid methyl esters can be obtained in high yield even in a catalyst-free reaction.

[0026] Referring to Figure 2, the reaction tower 20 is a tray-type reaction tower with multiple trays inside. Each tray is connected by a downcomer, and liquid flows from top to bottom. The reaction tower 20 consists of multiple tray units stacked vertically. Each tray unit has multiple (e.g., 4) trays. The configuration of the tray units is not limited and may include 1 to 5 trays.

[0027] Figure 3 is a schematic diagram showing the interior of the reaction tower of the manufacturing equipment according to this disclosure. The reaction tower 20 comprises a plurality of outer tanks 21a and 21b stacked vertically. Each of the outer tanks 21a and 21b constitutes a reaction stage. The even-numbered stages and odd-numbered stages of the reaction tower have similar configurations, and the even-numbered and odd-numbered stages are point-symmetrical. The dimensions of each outer tank (one reaction stage) may be 30 to 45 cm in height and 50 to 70 cm in diameter. When within this range, fatty acid esters can be produced efficiently in high yield.

[0028] Referring to Figure 3, the outer tanks 21a and 21b each constitute a reaction stage with a height of 40 cm and a diameter of 65 cm. The outer tank 21a comprises a first cylinder 22a rising from the bottom surface 25a of the outer tank 21a, and a second cylinder 23a that is shorter in height than the first cylinder 22a and also rises from the bottom surface 25a. Furthermore, inside the first cylinder 22a is a third cylinder 24a that penetrates the bottom surface 25a, with a portion protruding above the bottom surface and a portion protruding below the bottom surface. The first cylinder 22a is 38 cm high and 13 cm in diameter, and is a cylinder that rises to almost the full height of the outer tank 21a. The second cylinder 23a is 30 cm high and 13 cm in diameter, which is about 3 / 4 of the height of the outer tank 21a. The third cylinder 24a is positioned to protrude 25 cm above the bottom surface 25a and 37 cm below the bottom surface 25a. The lower part of the third cylinder 24a is positioned to be inserted into the second cylinder 23b, which is one level below it. In other words, the third cylinder 24a is positioned from inside the first cylinder 22a to inside the second cylinder 23b, which is one level below it.

[0029] The first cylinder 22a and the second cylinder 23a are positioned diagonally opposite each other near the periphery of the outer tank 21a. Multiple bubble bells 211a are provided between the first cylinder 22a and the second cylinder 23a.

[0030] The outer tank 21b, which is the reaction stage one level below the outer tank 21a, has the same configuration as the outer tank 21a. Inside the outer tank 21b, there is a first cylinder 22b rising from the bottom surface 25b and a second cylinder 23b rising from the bottom surface 25b. Furthermore, inside the first cylinder 22b, there is a third cylinder 24b that penetrates the bottom surface 25b, with a portion protruding above the bottom surface and a portion protruding below the bottom surface. The shapes of the first cylinder 22b, the second cylinder 23b, and the third cylinder 24b are the same as those of the outer tank 21a. Multiple bubble bells 211b are provided between the first cylinder 22b and the second cylinder 23b.

[0031] A downcomer is formed by the first cylinders 22a and 22b, the second cylinders 23a and 23b, and the third cylinders 24a and 24b. The height of the first cylinders 22a and 22b is greater than the protruding height of the third cylinders 24a and 24b, and extends to almost the full height of the outer tanks 21a and 21b, thereby ensuring contact time between the flowing liquid fatty acid and the rising methanol gas, without hindering the movement of methanol gas, and suppressing droplet entrainment.

[0032] The first cylinders 22a and 22b have notched holes 221a and 221b formed in the peripheral walls of the rising portions from the bottom surfaces 25a and 25b. The notched holes 221a and 221b are formed on the outer circumference of the peripheral wall, far from the center of the outer tank. The notched holes 221a and 221b are approximately 30 mm high and 80 mm wide. Liquid fatty acids flow into and out of the first cylinders 22a and 22b through the notched holes 221a and 221b. By providing the notched holes 221a and 221b far from the first cylinders 22a and 22b and the bubble bell 211, and on the outer circumference of the peripheral wall, the liquid does not short-circuit, and the residence time of the liquid can be ensured. The first cylinders 22a and 22b act as sheaths for the third cylinders 24a and 24b, and even if bumping occurs, the flow of unreacted liquid can be suppressed.

[0033] The second cylinders 23a and 23b have notched holes 231a and 231b formed in the peripheral walls of the rising portions from the bottom surfaces 25a and 25b. The notched holes 231a and 231b are semicircular holes with a radius of approximately 4 mm. Liquid fatty acids flow out of the second cylinders 23a and 23b through these notched holes 231a and 231b. By placing the notched holes 231a and 231b on the outer circumference side of the peripheral wall (closer to the outer tank), away from the first cylinders 22a and 22b and the bubble bell 211, the liquid does not short-circuit, and sufficient residence time for the liquid can be ensured.

[0034] The bubble bell body 211 consists of a cap with multiple elongated holes at its lower end and an inner cylinder housed inside the cap. The inner cylinder penetrates the bottom surface of the tray and is approximately half the height of the cap.

[0035] Figure 4 is a schematic diagram showing the interior of the reaction tower of the manufacturing equipment according to this disclosure. Figure 4 shows a horizontal cross-section of tray 21. A third cylinder 24 is positioned inside a first cylinder 22. The first cylinder 22 and the second cylinder 23 are positioned diagonally opposite each other. Sixteen bubble bells 211 are positioned between the first cylinder 22 and the third cylinder 24. In even-numbered and odd-numbered stages, the first cylinder 22 and the second cylinder 23 are positioned in opposite positions. The number of bubble bells provided in tray 21 can be set considering reaction efficiency, etc., and is not particularly limited, but it is preferably 10 to 24.

[0036] In reaction column 20, liquid fatty acids flow down from the top through a downcomer, and methanol gas rises from the bottom through a bubble bell. Fatty acid methyl esters and water are produced as the liquid fatty acids and methanol gas come into contact at each stage. The amount of water in the methanol gas increases towards the top of the reaction column, and the amount of fatty acid methyl esters in the liquid increases towards the bottom of the reaction column. The methanol gas dissolves in the liquid and functions as a reaction raw material, and as an rising gas, it also stirs the reaction mixture.

[0037] (Manufacturing method) The method for producing fatty acid methyl esters according to this disclosure is preferably carried out in the manufacturing equipment described above. The manufacturing method according to this disclosure will be explained with partial reference to Figure 1.

[0038] The method for producing fatty acid methyl esters includes an esterification step. In the esterification step, fatty acids are introduced from a first raw material tank 11 to the upper part of the reaction tower 20, and methanol is introduced from a second raw material tank 12 to the lower part of the reaction tower 20, and the fatty acids and methanol are brought into contact within the reaction tower 20. The fatty acids introduced into the reaction tower 20 are heated in a first heat exchanger 31 by heat exchange with the reactants (the product, fatty acid methyl esters) flowing through the piping 61 that is discharged from the reaction tower 20. The fatty acids introduced into the reaction tower 20 are further heated in a heater 32 and introduced into the reaction tower 20 at a temperature of approximately 260°C. The flow rate of the fatty acids is set according to the production volume, etc., but can be set to, for example, 800 to 1600 kg / h.

[0039] The methanol introduced into the reaction tower 20 is heated in the second heat exchanger 35 by heat exchange with the reflux product discharged from the reaction tower 20. The methanol introduced into the reaction tower 20 is vaporized in the evaporator 33 and further heated in the heater 34, and introduced into the reaction tower 20 at a temperature of approximately 270°C. The methanol flow rate is set according to the production volume, etc., but can be set to, for example, 230 to 480 kg / h. The ratio of methanol to fatty acid charged can be set to approximately 2.1 mol / 1 mol when the fatty acid is oleic acid. The ratio of the amount of fatty acid charged to the amount of methanol charged per unit time may be 1:1.8 to 1:3.0 (molar ratio), and 1:1.9 to 1:2.7 (molar ratio) is preferred. The amounts of fatty acid and methanol charged may be changed according to the overall situation of the manufacturing process. For example, if the acid value of the obtained fatty acid methyl ester is judged to be high, the methanol flow rate may be kept constant, and the relative supply of oleic acid may be reduced to about 80% of the amount used in a normal reaction. Also, during idling operation of the manufacturing equipment (a state in which the fatty acid methyl ester is not recovered and the raw materials are refluxed within the manufacturing equipment), the methanol flow rate may be kept constant, and the relative supply of oleic acid may be reduced to about 50% of the amount used in a normal reaction.

[0040] The inside of the reaction tower 20 may be under pressure, and can be set to, for example, about 0.87 MPa.

[0041] The esterification reaction may be carried out without a catalyst, or a catalyst may be used to improve the reaction rate. When a catalyst is used, iron catalysts, titanium catalysts such as tetra-n-butoxytitanium or titanium diisopropoxybis(triethanolamine), and tin catalysts such as dibutyltin oxide or di(2-ethylhexanoate)tin(II) can be used. For example, when using an iron catalyst, iron powder may be added to the fatty acid contained in the first raw material tank 11 as a catalyst addition step. From the viewpoint of catalyst separation from the product and avoiding clogging of the reaction equipment caused by solid catalysts, it is preferable to carry out the esterification reaction without a catalyst.

[0042] The fatty acids used in the production of fatty acid methyl esters may be animal-derived fatty acids or plant-derived fatty acids. It is preferable that the fatty acids include unsaturated fatty acids. The unsaturated fatty acids may be a mixture of oleic acid, linoleic acid, alpha-linolenic acid, gamma-linolenic acid, arachidonic acid, etc., and it is preferable that the fatty acids contain oleic acid as the main component. Here, "main component" means the component that makes up the largest amount of the fatty acids contained.

[0043] Using the manufacturing equipment described herein, fatty acid methyl esters can be obtained in high yield. The manufacturing process may be a continuous reaction. As an example, oleic acid was introduced into a reaction column at a flow rate of 1068 kg / h and methanol at a flow rate of 277 kg / h, and esterification was performed, resulting in the acquisition of fatty acid methyl esters with a yield of over 99%. The excess methanol refluxed and recovered from the top of the reaction column 20 was recovered in the distillation column 37, stored in the second raw material tank 12, and then reused as a raw material. The acid value of the product was 3.7 mgKOH / g. The manufacturing equipment described herein can stably produce fatty acid methyl esters with a sufficiently reduced acid value (specifically, an acid value of 7 mgKOH / g or less).

[0044] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the present invention is defined by the claims and is intended to include all modifications in the sense and scope equivalent to the claims. [Explanation of symbols]

[0045] 1 Manufacturing equipment, 11 First raw material tank, 12 Second raw material tank, 13 Product tank, 20 Reaction column, 21 Tray, 21a, 21b Outer tank, 22 (22a, 22b) First cylinder, 23 (23a, 23b) Second cylinder, 24 (24a, 24b) Third cylinder, 25a, 25b Bottom, 211 (211a, 211b) Bubble bell, 221 (221a, 221b), 231 (231a, 231b) Notch hole, 31 First heat exchanger, 32, 34 Heaters, 33 Evaporator, 35 Second heat exchanger, 36 Reflux drum, 37 Distillation column, 38 Pump, 39 Condenser, Piping for 41, 42, 51, 52, 61, 62, 71, 72, 73, and 75.

Claims

1. A first raw material tank for containing fatty acids, A second raw material tank containing methanol, A reaction tower having a first raw material supply line connected to the first raw material tank at the top and a second raw material supply line connected to the second raw material tank at the bottom, A removal line for removing the product from the aforementioned reaction tower, Equipped with, The aforementioned reaction tower is a bubble tower equipped with 40 to 55 reaction stages. The system includes a first heat exchanger that exchanges heat between the first raw material supply line and the extraction line. Manufacturing equipment for fatty acid methyl esters.

2. The aforementioned bubble tower consists of reaction stages, each 30-45 cm high and 50-70 cm in diameter, stacked vertically. Each of the above reaction stages is A first cylinder rising from the bottom surface of the reaction stage, A second cylinder rises from the bottom surface of the reaction stage and is shorter in height than the first cylinder, A third cylinder is positioned inside the first cylinder, penetrates the bottom surface of the reaction stage, and has a portion that protrudes upward from the bottom surface and a portion that protrudes downward from the bottom surface. Equipped with, The third cylinder is positioned to be inserted into the second cylinder of the reaction stage one level below. The production apparatus for fatty acid methyl esters according to claim 1.

3. Each of the first cylinder and the second cylinder is, A notched hole is formed in the peripheral wall of the rising portion from the bottom surface of the reaction stage. The production apparatus for fatty acid methyl esters according to claim 2.

4. Each of the reaction stages comprises 10 to 24 bubble bells. A production apparatus for fatty acid methyl esters according to claim 1 or claim 2.

5. A method for producing fatty acid methyl esters in a fatty acid methyl ester production facility according to claim 1 or claim 2, The process includes an esterification step in which a fatty acid is introduced from the first raw material tank into the reaction tower, and methanol is introduced from the second raw material tank into the reaction tower, and the fatty acid and methanol are brought into contact within the reaction tower. In the first heat exchanger, After the esterification step, the reaction product is discharged from the reaction tower and flows through the extraction line, A method for producing fatty acid methyl esters, wherein heat exchange is performed with fatty acids that are discharged from the first raw material tank and flow through the first raw material supply line.

6. The process includes adding iron powder to the fatty acid contained in the first raw material tank, A method for producing a fatty acid methyl ester according to claim 5.

7. In the esterification step, The ratio of the amount of fatty acid charged to the reaction tower per unit time to the amount of methanol charged to the reaction tower is 1:1.8 to 1:3.0 (molar ratio). A method for producing a fatty acid methyl ester according to claim 6.

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