Castor oil refining method, alkali refining device and refining system

Abstract

The invention discloses a refining method, an alkali refining device and a refining system for castor oil, and belongs to the technical field of castor oil processing. The method includes alkali refining, decolorization and deodorization. Before alkali refining, oil residue is removed by filter pressing, and the filter pressing temperature is 82-86°C; sampling is performed at 50-60°C and the acid value is detected, and then the alkali refining process is performed; if the acid value is less than 4, the alkali refining process includes: heating the oil to 40-50°C, adding 70-80wt% phosphoric acid and spraying a sodium hydroxide solution with a concentration of 3-6wt on the oil surface for 12-18 minutes according to the acid value, stirring while spraying, continuing to stir for 10-15 minutes after spraying, then heating to 50-55°C, standing for 10-15 minutes, then heating to 60-65°C and centrifuging, and finally sending to the decolorization process; if the acid level is greater than or equal to 4, the alkali refining process includes soap removal, salt water washing, pure water washing, upper oil washing and dehydration.

Description

Technical Field

[0001] The invention belongs to the technical field of castor oil processing, and particularly relates to a castor oil refining method, an alkali refining device and a refining system. Background Art

[0002] Castor oil is an oil obtained by pressing and refining the mature seeds of the Euphorbiaceae plant Ricinus communis. Castor oil contains about 85% ricinoleic acid, which is the only oil mainly composed of hydroxyl acids. Compared with other vegetable oils, castor oil has the characteristics of high hydroxyl value and high acyl value. The main component of castor oil is triglyceride of higher fatty acids. The main component of castor oil fatty acids is ricinoleic acid, which accounts for 89% of the total mass fraction of fat, linoleic acid accounts for 4.2%, oleic acid accounts for 3.0%, stearic acid accounts for 1.0%, palmitic acid accounts for 1.0%, linolenic acid accounts for 0.3%, and dihydroxystearic acid accounts for 0.7%. Castor oil is a widely used chemical raw material that can be used to make synthetic resins, coatings, lubricants and plasticizers, etc. It can also be used as an auxiliary material in the pharmaceutical, printing and dyeing and leather industries.

[0003] Compared with other vegetable oils, castor oil has higher viscosity and is easier to emulsify during alkali refining. The refining process of castor oil usually includes alkali refining, water washing, dehydration, decolorization and deodorization.

[0004] For example, the patent application number CN201510378480.X discloses a method for refining castor oil, which includes the following steps:

[0005] Alkali refining: first calculate the amount of alkali to be added according to the acid value of the crude oil and prepare an alkali solution with a concentration of about 3‰, adjust the crude oil temperature to 30-40℃, add the prepared alkali solution, and add all the alkali solution at once within 15 minutes, and stir quickly at about 60r / min. After adding the alkali solution, continue stirring for 10-20 minutes. When the oil soap begins to separate, increase the temperature at a rate of 1℃ per minute, and reduce the stirring speed to about 30r / min. After the oil soap temperature rises to 85-90℃, stop stirring, add 25% of the oil weight and hot water at a temperature above 90℃, and let it settle for 15-20 minutes.

[0006] Water washing: transfer the upper semi-clean oil into the washing pot, heat it to 85-90℃, and then wash it with hot water of the same oil temperature. Wash it 2-3 times, stirring at about 30r / min for 3-5min. The amount of water used each time is 15-20% of the oil weight. After each addition of water, let it settle for 30-50min before releasing the washing wastewater.

[0007] Decolorization: alkali-refined and dehydrated castor oil is decolorized with dry activated clay and activated carbon. The decolorization temperature is 90-95°C, the absolute pressure is below 8KPa, and the time at the specified operating temperature is about 20 minutes. After the decolorization is completed, it is cooled to 70-80°C and filtered to obtain refined and decolorized castor oil.

[0008] Deodorization: Due to the characteristics of ricinoleic acid in castor oil, the deodorization temperature should not be too high, and the vacuum degree requirement is very high. Generally, the deodorization temperature is controlled at 140-160℃, the absolute pressure is below 0.67kPa, the deodorization time is 4-6h, and the deodorized oil is released after cooling to 70-80℃.

[0009] For example, the patent application number CN88104649.3 discloses an alkali refining method for refining castor oil, which comprises: placing crude oil in an alkali refining tank, measuring its acid value, stirring the oil to be uniform, heating the crude oil to control the oil temperature at 25-30°C, spraying the required alkali solution evenly on the oil surface within 20-30 minutes, continuing to stir for 15 minutes, standing for more than 10 minutes, starting to stir and heat, and controlling the heating rate at 1°C / minute. When the oil temperature rises to 80°C, , stop heating and stirring, let it stand for 80-120 minutes to release soap nuts for processing, spray boiling water on the oil surface, stop watering after the oil surface rises 110 cm, let it stand for 40-50 minutes, and release the initial washing water into the oil-water separation tank, repeat the above operation once, use continuous water washing method to spray water, use pH test paper to check the pH of the discharged water = 7, stop spraying, let it stand for 40 minutes, release the waste water into the oil-water separation tank, and the semi-finished product is vacuum-absorbed into the evaporator. Heat the oil to 93-97℃ under a vacuum degree of 0.089Mpa to remove moisture.

[0010] It can be seen from the above process that water washing is required after alkali refining, which will produce a large amount of wastewater and is difficult to treat; in addition, water washing will consume a lot of time. Summary of the invention

[0011] In order to solve the above problems, the present invention provides a castor oil refining method, alkali refining device and refining system. The applicant found that under the condition of low acid value, anhydrous alkali refining method can be used; under the anhydrous alkali refining method, the wastewater discharge is small and the treatment time is short, but the treatment effect is similar to or better than that of the conventional method. The technical scheme is as follows:

[0012] On the one hand, an embodiment of the present invention provides a method for refining castor oil, including alkali refining, decolorization and deodorization. Before alkali refining, oil residue is removed by filter pressing, and the filter pressing temperature is 82-86° C.; sampling is performed at 50-60° C. and the acid value is detected, and then an alkali refining process is performed; if the acid value is less than 4, the alkali refining process includes: heating the oil to 40-50° C., adding 70-80wt% phosphoric acid and spraying a sodium hydroxide solution with a concentration of 3-6wt% on the oil surface for 12-18 minutes according to the acid value, stirring while spraying, continuing to stir for 10-15 minutes after spraying, then heating to 50-55° C., standing for 10-15 minutes, and then heating to 60-65° C. and centrifuging, and finally sending to the decolorization process; wherein, the amount of phosphoric acid used is 0.05-0.2% of the oil mass; if the acid value is greater than or equal to 4, the alkali refining process includes:

[0013] S201 Soap removal: Spray 3-6wt% sodium hydroxide solution on the oil surface at 25-30℃ according to the acid value for 10-15 minutes, stir while spraying, continue stirring for 10-15 minutes after spraying, let stand for 20-25 minutes, raise the temperature to 80-85℃ at 0.8-1.2℃ / min, let stand for 60-80 minutes, release the soap stock and washing water;

[0014] S202 brine washing: heat the oil to 90-95°C, spray boiling sodium chloride solution on the oil surface, the amount of sodium chloride solution is 5-10% of the oil volume, and stir while spraying; after spraying, let it stand for 45-60 minutes, release the washing water; repeat several times until the pH of the washing water reaches 7; the concentration of the sodium chloride solution is 25-31wt%;

[0015] S203 pure water washing: under vacuum conditions, add boiling water to the oil, the amount of boiling water is 0.4-0.5 times the volume of the oil, stir for at least 10 minutes, let it stand for 10-15 minutes, and release the washing water; repeat the above process several times and take the upper layer of oil;

[0016] S204 upper oil washing: the upper oil is washed with water, the washing process is: the oil temperature is 90-95°C, the washing water temperature is 90-95°C, the water amount for each washing is 10-15% of the volume of the upper oil, after the washing is completed, let it stand for 30-45 minutes, and release the washing water; repeat the above process several times;

[0017] S205 Dehydration: Combine the lower layer oil obtained in step S203 and the upper layer oil after washing in step S204, and dehydrate at 90-95° C. under vacuum.

[0018] Wherein, when the acid value is less than 4 and in step S201, before adding the sodium hydroxide solution, the stirring speed is greater than 50 r / min; after adding the sodium hydroxide solution, the stirring speed is less than 30 r / min.

[0019] Wherein, in step S203 and step S205, the vacuum condition is 0.06-0.09 MPa.

[0020] Specifically, in step S203, the number of water washings is 2 times; and in step S204, the number of water washings is 3 times.

[0021] Specifically, when the acid value is less than 4, the oil is heated to 40-50° C. by a first heater, the oil is mixed with phosphoric acid by a mixer, the sodium hydroxide solution is reacted with the oil in a spray reactor, the oil is heated to 50-55° C. in a heating reactor, the oil is heated to 60-65° C. by a second heater, and centrifuged by a high-speed centrifuge.

[0022] Specifically, when the acid value is greater than or equal to 4, the sodium hydroxide solution is reacted with the oil in the spray reactor, the oil is heated to 80-85° C. in the heating reactor, and the soap stock and the washing water are separated in the first oil-water separator; step S202 is performed in the first water washing kettle, and the washing water is released in the second oil-water separator; step S203 is performed in the second water washing kettle, and the oil layer is separated and the washing water is released in the liquid separator; step S204 is performed in the third water washing kettle, and the washing water is released in the third oil-water separator; step S205 is performed in the dehydration reactor.

[0023] On the other hand, the present invention provides an alkali refining device for castor oil, which includes a first heater, a mixer, a spray reactor, a heating reactor, a first oil-water separator, a first water washing kettle, a second oil-water separator, a second water washing kettle, a liquid separator, a dehydration reactor, a second heater, a high-speed centrifuge, a third water washing kettle, a third oil-water separator, a sodium hydroxide solution supply structure, a phosphoric acid supply structure, a sodium chloride solution supply structure, a pure water supply structure and a vacuum structure; the feed port of the spray reactor is connected to the mixer and the raw acid storage tank through a pipeline, the mixer is connected to the phosphoric acid supply structure and the outlet of the first heater through a pipeline, the inlet of the first heater is connected to the raw acid storage tank, and the discharge port of the spray reactor is connected to the heating reactor through a pipeline; the heating reactor outputs in two ways, one way is output to the feed port of the second heater, and the other way is output to the first oil-water separator; the discharge port of the second heater, the high-speed centrifuge The centrifuge and the decolorization reactor are connected in sequence through pipelines, and the first oil-water separator, the first water washing kettle, the second oil-water separator, the second water washing kettle and the liquid separator are connected in sequence through pipelines; the liquid separator is divided into two outputs, one output to the dehydration reactor, and the other output to the third water washing kettle; the third water washing kettle, the third oil-water separator and the dehydration reactor are connected in sequence through pipelines, and the dehydration reactor is connected to the decolorization reactor through a pipeline; a heating structure is provided in the sodium chloride solution supply structure and the pure water supply structure, the pure water supply structure is connected to the second water washing kettle and the third water washing kettle through a pipeline, the vacuum structure is connected to the second water washing kettle and the dehydration reactor through a pipeline, a first spray mechanism is provided in the upper part of the spray reactor, the first spray mechanism is connected to the sodium hydroxide solution supply structure through a pipeline, a second spray mechanism is provided in the first water washing kettle, and the second spray mechanism is connected to the sodium chloride solution supply structure through a pipeline.

[0024] Among them, the first spray mechanism in the embodiment of the present invention includes multiple groups of spray pipes; the spray pipes are arranged horizontally, located above the liquid surface, and connected to the sodium hydroxide solution supply structure through a pipeline with a valve.

[0025] On the other hand, the present invention provides a castor oil refining system, which includes a decolorizing device, a deodorizing device, a filter press, a crude acid storage tank and the aforementioned alkali refining device, wherein the filter press, the crude acid storage tank, the decolorizing device and the deodorizing device are sequentially connected by pipelines.

[0026] The present invention has the following advantages:

[0027] (1) According to the acid value of castor oil, different alkali refining methods are used, which is more flexible and can be selected according to customer requirements. If the customer has low requirements on product quality, anhydrous alkali refining can be used.

[0028] (2) Under the anhydrous alkali refining method, the wastewater discharge is small and the treatment time is short, but the treatment effect is similar to or better than that of the conventional method.

[0029] (3) In the water washing process, the product is washed with salt water, washed with pure water and washed with upper oil in sequence. By adopting a special water washing method, only the upper oil layer needs to be washed with water in the last step, which can reduce the discharge of wastewater.

[0030] (4) Sodium hydroxide solution and sodium chloride solution are added by spraying to improve the alkali refining effect and make stirring easier (castor oil has high viscosity and is easy to emulsify. If sodium hydroxide solution is added all at once, it is particularly easy to emulsify and difficult to stir).

[0031] (5) In fact, conventional methods usually use 10wt% sodium hydroxide solution to alkali-refine vegetable oils, and the higher the concentration, the better the effect. However, the applicant unexpectedly discovered that only for castor oil (the higher the alkali concentration of other common vegetable oils, the better), the treatment effect of 3-6wt% sodium hydroxide solution is better than the alkali refining effect of higher concentrations of sodium hydroxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a functional block diagram of the castor oil alkali refining unit. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] Example 1

[0035] Example 1 provides a method for refining castor oil, including alkali refining, decolorization and deodorization. Before alkali refining, the oil residue is removed by filter pressing (solid content is controlled to be less than 0.1%), and the filter pressing temperature is 85° C. Samples are taken at 60° C. (low viscosity) and the acid value is tested, and then the alkali refining process is performed.

[0036] If the acid value is less than 4 (in mgKOH / g, the same below), the alkali refining process includes: heating the oil to 45°C, adding 70wt% phosphoric acid and spraying 5wt% sodium hydroxide solution on the oil surface within 15 minutes according to the acid value, stirring while spraying, and the stirring speed is 60r / min; after spraying, continue stirring for 10 minutes, and the stirring speed is 30r / min; then heat to 55°C, let stand for 10 minutes, and then heat to 60°C (easy to centrifuge at this temperature) and centrifuge, and finally send to the decolorization process; wherein, the amount of phosphoric acid used is 0.1% of the oil mass.

[0037] If the acid value is greater than or equal to 4, the alkali refining process includes:

[0038] S201 desoaping: spray 5wt% sodium hydroxide solution on the oil surface at 25℃ according to the acid value within 15 minutes, stirring while spraying at a speed of 60r / min; continue stirring for 10 minutes after spraying, stirring at a speed of 20r / min, let it stand for 20 minutes, then heat to 85℃ at a speed of 1℃ / min, let it stand for a second time for 65 minutes, release the soap stock and washing water.

[0039] S202 Salt water washing: Heat the oil to 95℃, spray boiling sodium chloride solution on the oil surface, the amount of sodium chloride solution is 7% of the oil volume, stir while spraying, the stirring speed is 60r / min. After spraying, let it stand for 60 minutes and release the washing water. Repeat several times (usually 2-3 times) until the pH of the washing water reaches 7. The concentration of sodium chloride solution is 30wt%.

[0040] S203 pure water washing: add boiling water to the oil at 0.09MPa, the amount of boiling water is 0.4 times the volume of the oil, stir for 30 minutes, let stand for 10 minutes, and release the washing water. Repeat the above process twice and take the upper layer of oil (accounting for 40-60% of the total volume of the oil).

[0041] S204 upper oil washing: the upper oil is washed with water, the washing process is: the oil temperature is 95℃, the washing water temperature is 95℃, the amount of water used for each washing is 10% of the volume of the upper oil, after the washing is completed, let it stand for 30 minutes and release the washing water; repeat the above process 3 times.

[0042] S205 Dehydration: Combine the lower layer oil obtained in step S203 and the upper layer oil after water washing in step S204, and dehydrate at 90°C and 0.08MPa.

[0043] In the crude castor oil processing process, in most cases the acid value of the crude oil is greater than or equal to 4, but there is a possibility that the acid value of the crude oil is less than 4.

[0044] The indicators of castor oil treated by the method disclosed in this patent (both decolorization and deodorization adopt conventional processes) are: having the unique aroma of castor oil, acid value <2.0 mgKOH / g, impurities ≤0.05%, transparent, and slightly yellow in color (Y <20, R <1.5).

[0045] If the alkali refining process uses a process with an acid value less than 4 regardless of the acid value, the results after alkali refining are shown in Table 1:

[0046] Table 1

[0047]

[0048] If the alkali refining process adopts the process when the acid value is greater than or equal to 4 regardless of the acid value, the results after alkali refining are shown in Table 2:

[0049] Table 2

[0050]

[0051] It can be seen from Table 1 and Table 2 that the anhydrous alkali refining method has better effect at low acid value, but the effect is not as good as the conventional water washing method at high acid value. In addition, under low acid value and anhydrous alkali refining method, although the moisture content will increase slightly, the increase is not large; at the same time, although phosphoric acid is added to assist in desoaping, the phosphorus element will be separated with the soap, and the phosphorus element will not be significantly increased.

[0052] Comparative Example 1

[0053] In step S203, the mixture is washed with water for 5 times, and step S204 is omitted, i.e., vacuum dehydration is performed directly without separation. The comparison results with the method of this patent are shown in Table 3:

[0054] Table 3

[0055]

[0056] From Table 3, it can be seen that the effects of this process are not much different from those of Comparative Example 1, but at least 10% less wastewater is produced.

[0057] Example 2

[0058] See also Figure 1Embodiment 2 provides a kind of alkali refining device of castor oil, and the device comprises a first heater, a mixer, a spray reactor, a heating reactor, a first oil-water separator, a first water washing kettle, a second oil-water separator, a second water washing kettle, a liquid separator, a dehydration reactor, a second heater, a high-speed centrifuge, a third water washing kettle, a third oil-water separator, a sodium hydroxide solution supply structure, a phosphoric acid supply structure, a sodium chloride solution supply structure, a pure water supply structure and a vacuuming structure, etc. The sodium hydroxide solution supply structure is used to supply 3-6wt% of sodium hydroxide solution, the phosphoric acid supply structure is used to supply 70-80wt% of phosphoric acid, the sodium chloride solution supply structure is used to supply 25-31wt% of sodium chloride solution, the pure water supply structure supplies pure water, and the vacuuming structure is used to vacuumize. The feed port of the spray reactor is connected to the mixer and the crude acid storage tank through a pipeline, the mixer is connected to the phosphoric acid supply structure and the outlet of the first heater through a pipeline, the inlet of the first heater is connected to the crude acid storage tank, and the discharge port of the spray reactor is connected to the heating reactor through a pipeline. That is, the crude acid storage tank outputs in two ways according to the acid value of the crude acid. If the acid value is high, it is output to the spray stirring kettle (corresponding to the water washing method), and if the acid value is low, it is output to the first heater (corresponding to the anhydrous alkali refining method). The heating reactor outputs in two ways, one is output to the feed port of the second heater (corresponding to the anhydrous alkali refining method), and the other is output to the first oil-water separator (corresponding to the water washing method). The discharge port of the second heater, the high-speed centrifuge and the decolorization reactor are connected in sequence through pipelines. The first oil-water separator, the first water washing kettle, the second oil-water separator, the second water washing kettle and the liquid separator are connected in sequence through pipelines. The liquid separator outputs in two ways, one (corresponding to the lower part of the liquid separator) is output to the dehydration reactor, and the other (corresponding to the upper part of the liquid separator) is output to the third water washing kettle. The third water washing kettle, the third oil-water separator and the dehydration reactor are connected in sequence through pipelines, and the dehydration reactor is connected to the decolorization reactor through pipelines. The sodium chloride solution supply structure and the pure water supply structure are both provided with heating structures to heat the solutions therein to boiling. The pure water supply structure is connected to the second water washing kettle and the third water washing kettle through pipelines, and the vacuum structure is connected to the second water washing kettle and the dehydration reactor through pipelines. A first spray mechanism is provided in the upper part of the spray reactor, and the first spray mechanism is connected to the sodium hydroxide solution supply structure through pipelines. A second spray mechanism is provided in the first water washing kettle, and the second spray mechanism is connected to the sodium chloride solution supply structure through pipelines.

[0059] Among them, the first spray mechanism in the embodiment of the present invention includes multiple groups of spray pipes. The spray pipes are arranged horizontally, located above the liquid surface, connected to the sodium hydroxide solution supply structure through a pipeline with a valve, and spray holes are arranged on the lower side. The multiple groups of spray pipes are evenly distributed. The second spray mechanism is similar to the first spray mechanism, and a detailed description is omitted in this embodiment.

[0060] Among them, the spray reactor, heating reactor, first water washing reactor, second water washing reactor and dehydration reactor in this embodiment can be realized by one or more reactors (equipped with a stirrer, heating structure or vacuum structure, etc. as needed); the first oil-water separator, the second oil-water separator and the third oil-water separator can be realized by one or more oil-water separators.

[0061] Specifically, see Figure 1 If the acid value is less than 4, the oil is heated to 40-50°C by a first heater, the oil is mixed with phosphoric acid by a mixer, the sodium hydroxide solution is reacted with the oil in a spray reactor, the oil is heated to 50-55°C in a heating reactor, the oil is heated to 60-65°C by a second heater, and centrifuged by a high-speed centrifuge.

[0062] Specifically, see Figure 1 When the acid value is greater than or equal to 4, the sodium hydroxide solution is reacted with the oil in the spray reactor, the oil is heated to 80-85°C in the heating reactor, and the soap stock and the washing water are separated in the first oil-water separator; step S202 is performed in the first water washing kettle, and the washing water is released in the second oil-water separator; step S203 is performed in the second water washing kettle, and the oil layer is separated and the washing water is released in the liquid separator; step S204 is performed in the third water washing kettle, and the washing water is released in the third oil-water separator; step S205 is performed in the dehydration reactor.

[0063] Among them, pumps, valves or flow meters, etc. are set on the pipeline in the embodiment of the present invention as needed; "first", "second" or "third" in this embodiment only serves to distinguish and has no other special meaning.

[0064] Example 3

[0065] Example 3 provides a castor oil refining system, which includes a decolorizing device, a deodorizing device, a filter press, a crude acid storage tank, and the alkali refining device disclosed in Example 2, etc. The filter press, the crude acid storage tank, the decolorizing device and the deodorizing device are connected in sequence through pipelines, and a heater needs to be provided on the feed port of the filter press to heat the oil to 82-86°C.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for refining castor oil, comprising alkali refining, decolorization and deodorization, characterized in that: Before alkali refining, remove the oil residue by filter pressing at a temperature of 82-86°C; take samples at 50-60°C and test the acid value before carrying out the alkali refining process; If the acid value is less than 4, the alkali refining process includes: heating the oil to 40-50°C, adding 70-80wt% phosphoric acid and spraying a sodium hydroxide solution with a concentration of 3-6wt% on the oil surface for 12-18 minutes according to the acid value, stirring while spraying, continuing to stir for 10-15 minutes after spraying, then heating to 50-55°C, standing for 10-15 minutes, then heating to 60-65°C and centrifuging, and finally sending to the decolorization process; wherein, the amount of phosphoric acid used is 0.05-0.2% of the oil mass; If the acid value is greater than or equal to 4, the alkali refining process includes: S201 Soap removal: Spray 3-6wt% sodium hydroxide solution on the oil surface at 25-30℃ according to the acid value for 10-15 minutes, stir while spraying, continue stirring for 10-15 minutes after spraying, let stand for 20-25 minutes, raise the temperature to 80-85℃ at 0.8-1.2℃ / min, let stand for 60-80 minutes, release the soap stock and washing water; S202 salt water washing: heat the oil to 90-95℃, spray boiling sodium chloride solution on the oil surface, the amount of sodium chloride solution is 5-10% of the oil volume, and stir while spraying; after spraying, let it stand for 45-60 minutes, release the washing water; repeat several times until the pH of the washing water is 7; the concentration of the sodium chloride solution is 25-31wt%; S203 pure water washing: under vacuum conditions, add boiling water to the oil, the amount of boiling water is 0.4-0.5 times the volume of the oil, stir for at least 10 minutes, let it stand for 10-15 minutes, and release the washing water; repeat the above process several times and take the upper layer of oil; S204 upper oil washing: the upper oil is washed with water, the washing process is: the oil temperature is 90-95°C, the washing water temperature is 90-95°C, the water amount for each washing is 10-15% of the volume of the upper oil, after the washing is completed, let it stand for 30-45 minutes, and release the washing water; repeat the above process several times; S205 Dehydration: Combine the lower layer oil obtained in step S203 and the upper layer oil after washing in step S204, and dehydrate at 90-95° C. under vacuum.

2. The method for refining castor oil according to claim 1, characterized in that: When the acid value is less than 4 and in step S201, before adding the sodium hydroxide solution, the stirring speed is greater than 50 r / min; after adding the sodium hydroxide solution, the stirring speed is less than 30 r / min.

3. The method for refining castor oil according to claim 1, characterized in that: In step S203 and step S205, the vacuum condition is 0.06-0.09 MPa.

4. The method for refining castor oil according to claim 1, characterized in that: In step S203, the number of water washings is 2 times; in step S204, the number of water washings is 3 times.

5. The method for refining castor oil according to claim 1, characterized in that: When the acid value is less than 4, the oil is heated to 40-50°C by a first heater, the oil is mixed with phosphoric acid by a mixer, the sodium hydroxide solution is reacted with the oil in a spray reactor, the oil is heated to 50-55°C in a heating reactor, the oil is heated to 60-65°C by a second heater, and centrifuged by a high-speed centrifuge.

6. The method for refining castor oil according to claim 5, characterized in that: When the acid value is greater than or equal to 4, the sodium hydroxide solution is reacted with the oil in the spray reactor, the oil is heated to 80-85°C in the heating reactor, and the soap stock and the washing water are separated in the first oil-water separator; step S202 is performed in the first water washing kettle, and the washing water is released in the second oil-water separator; step S203 is performed in the second water washing kettle, and the oil layer is separated and the washing water is released in the liquid separator; step S204 is performed in the third water washing kettle, and the washing water is released in the third oil-water separator; step S205 is performed in the dehydration reactor.

7. An alkali refining device for castor oil using the refining method as claimed in claim 6, characterized in that: The invention comprises a first heater, a mixer, a spray reactor, a heating reactor, a first oil-water separator, a first water washing kettle, a second oil-water separator, a second water washing kettle, a liquid separator, a dehydration reactor, a second heater, a high-speed centrifuge, a third water washing kettle, a third oil-water separator, a sodium hydroxide solution supply structure, a phosphoric acid supply structure, a sodium chloride solution supply structure, a pure water supply structure and a vacuum structure; the feed port of the spray reactor is connected to the mixer and the crude acid storage tank through a pipeline, the mixer is connected to the phosphoric acid supply structure and the outlet of the first heater through a pipeline, the inlet of the first heater is connected to the crude acid storage tank, the discharge port of the spray reactor is connected to the heating reactor through a pipeline; the heating reactor is divided into two outputs, one output to the feed port of the second heater, and the other output to the first oil-water separator; the discharge port of the second heater, the high-speed centrifuge and the decolorization reactor are connected to the heating reactor through a pipeline. The first oil-water separator, the first water washing kettle, the second oil-water separator, the second water washing kettle and the liquid separator are connected in sequence through pipelines; the liquid separator is divided into two outputs, one output to the dehydration reactor, and the other output to the third water washing kettle; the third water washing kettle, the third oil-water separator and the dehydration reactor are connected in sequence through pipelines, and the dehydration reactor is connected to the decolorization reactor through a pipeline; the sodium chloride solution supply structure and the pure water supply structure are both provided with a heating structure, the pure water supply structure is connected to the second water washing kettle and the third water washing kettle through a pipeline, the vacuum structure is connected to the second water washing kettle and the dehydration reactor through a pipeline, the first spray mechanism is provided in the upper part of the spray reactor, the first spray mechanism is connected to the sodium hydroxide solution supply structure through a pipeline, the first water washing kettle is provided with a second spray mechanism, and the second spray mechanism is connected to the sodium chloride solution supply structure through a pipeline.

8. The alkali refining device according to claim 7, characterized in that: The first spray mechanism comprises a plurality of spray pipes; the spray pipes are arranged horizontally, are located above the liquid surface, and are connected to the sodium hydroxide solution supply structure through pipelines with valves.

9. A castor oil refining system comprising a decolorizing device and a deodorizing device, characterized in that: It also includes a filter press, a crude acid storage tank and an alkali refining device as described in any one of claims 7-8, wherein the filter press, the crude acid storage tank, the decolorization device and the deodorization device are connected in sequence through pipelines.

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