CN113416604A

CN113416604A - Method for carrying out alkali treatment, alkali refining and refining on crude oil by virtue of supergravity technology

Info

Publication number: CN113416604A
Application number: CN202110615617.4A
Authority: CN
Inventors: 孙东哲; 张亮亮; 王满意; 初广文; 酉琳娜; 陈建峰; 王翔宇
Original assignee: Beijing University of Chemical Technology; Cofco Nutrition and Health Research Institute Co Ltd
Current assignee: Beijing University of Chemical Technology; Cofco Nutrition and Health Research Institute Co Ltd
Priority date: 2021-06-02
Filing date: 2021-06-02
Publication date: 2021-09-21

Abstract

The invention provides a method for carrying out alkali treatment, alkali refining and refining on edible vegetable crude oil by a supergravity technology. The method can realize the quick and sufficient contact of the crude oil and the alkali liquor, quickly neutralize free acid in the crude oil, and avoid oil product loss and nutrient loss caused by contact during the production of the oil product and the alkali liquor in the prior art. The invention can be suitable for various alkali liquor concentrations, various crude oils and various working conditions, can simply save part of process steps according to actual conditions, and has wide industrial application prospect.

Description

Method for carrying out alkali treatment, alkali refining and refining on crude oil by virtue of supergravity technology

Technical Field

The invention relates to a method for carrying out alkali treatment, alkali refining and refining on edible vegetable crude oil by a supergravity technology.

Background

In the field of edible plant crude oil production, oil refining generally refers to a process of removing harmful impurities in crude oil (extracted primary oil) which are not beneficial to eating, storage, production and the like. Deacidification is one of important links in the oil refining process, and the main purpose of deacidification is to neutralize free fatty acid in crude oil by acid-base chemical reaction. The deacidification method comprises various methods such as alkali refining, distillation, solvent extraction, esterification and the like. The most widely used in industrial production are the alkali refining process and the steam distillation process (i.e., physical refining process).

The alkali refining deacidification method is a refining method for neutralizing free fatty acid in grease by alkali. The alkali used for neutralizing the free fatty acid includes sodium hydroxide (commonly known as caustic soda or caustic soda), sodium carbonate (soda ash), calcium hydroxide, and the like. The general industrial production of oil and fat adopts sodium hydroxide and sodium carbonate, or uses sodium carbonate first and then uses sodium hydroxide, wherein the application of the sodium hydroxide is the most extensive at home and abroad.

The main functions of the alkali refining deacidification process can be summarized as the following two points: 1) the caustic soda can neutralize most of free fatty acid in crude oil, and the produced sodium salt (sodium soap) of fatty acid is not easy to dissolve in oil and becomes flocculent and precipitates. 2) The sodium soap generated by neutralization is a surface active substance and has strong adsorption capacity, so that other impurities, such as protein, mucus, pigment, phospholipid, substances with hydroxyl or phenolic groups, and even suspended solid impurities can be adsorbed, and are carried by flocculent soap groups, so that the sodium soap is separated from an oil phase. It must be noted that the saponification reaction of caustic soda and small amounts of triglycerides (neutral oils) leads to an increase in refining costs. Therefore, the optimum operating conditions are selected in the production to obtain the desired yield.

In the process of grease alkali refining and deacidification, alkali liquor is hoped to fully capture free fatty acid in the vegetable crude oil, and the contact time of the alkali liquor and triglyceride is hoped not to be too long, so that excessive saponification reduces the grease yield. In addition, in the process of alkali refining and deacidification, the crude oil is in an alkali liquor environment and a thermal environment for a long time, so that the problems of loss of nutrient substances such as tocopherol, phytosterol and the like in the oil product and acid reversion and color reversion of the oil product are easily caused. How to carry out the alkali refining deacidification process of the crude oil quickly and efficiently, reduce the loss of nutrient substances in the crude oil treatment process and avoid long-time heat treatment so as to avoid the problem of acid returning and color returning which always troubles the food industry. Meanwhile, the existing edible plant crude oil deacidification equipment has the defects of large occupied area, heavy weight, high energy consumption, long semi-continuous treatment time and the like, so that the production efficiency is low and the economic benefit is poor.

Aiming at the technical difficulties, the inventor of the invention creatively uses the supergravity technology in the alkali refining process of the edible vegetable crude oil through a great deal of research and optimization, and obtains very ideal effect. The super-gravity rotating bed simulates a super-gravity environment through centrifugal force generated by rotation to strengthen the transfer and reaction processes, and can greatly improve the efficiency of the transfer and reaction processes. At present, this technology has been expanded from the initial application to processes of rectification, absorption, etc. to a number of fields of chemical reaction, ultrafine particle preparation, etc., and structures regarding supergravity devices have been disclosed in earlier patents (application nos. 91111028.3, 91109255.2, 01268009.5, 200520100685.3, 02114174.6, 200510032296.6, 201610515008.0, 201910053047.7, 201910711393. X).

Disclosure of Invention

In view of the above problems, the present invention provides a method for alkali treatment, alkali refining and refining of crude edible vegetable oil by a supergravity technique.

In one embodiment of the present invention, a method for alkali-adding treatment of edible crude vegetable oil by a supergravity technique is provided. In a preferred embodiment, the alkali addition treatment is carried out as a continuous reaction. In another preferred embodiment, the alkali treatment is carried out at a hypergravity level of from 27 to 171g, preferably from 62 to 110 g. In another preferred embodiment, the alkali addition treatment is carried out using 6 to 15 baume NaOH. In another preferred embodiment, the alkali treatment is carried out at a temperature of 55 to 95 deg.C, preferably 65 to 75 deg.C. In another preferred embodiment, the alkali treatment is carried out with an excess of alkali of-5% to 25%, preferably 5% -15%. In another preferred embodiment, the edible crude vegetable oil is selected from one or more of the group consisting of soybean crude oil, rapeseed crude oil, peanut crude oil, corn crude oil, and sunflower seed crude oil.

In another embodiment of the present invention, a method for alkali refining edible crude vegetable oil is provided, wherein the alkali refining comprises the steps of acidification, alkali addition treatment, water washing, drying, etc., and the alkali addition treatment step is performed by using the alkali addition treatment method of the present invention. In a preferred embodiment, the acidification step is carried out with an excess of acid of 0 to 40%, preferably 10 to 20%.

In another embodiment of the present invention, another method for alkali refining edible crude vegetable oil is provided, wherein the alkali refining comprises the steps of acidification, alkali treatment, drying and the like, wherein the alkali treatment step is performed by using the alkali treatment method of the present invention, and a separate water washing step is not required after the alkali treatment step. Preferably, this embodiment of the invention is carried out using 6-9 baume NaOH.

In another embodiment of the present invention, another method for alkali refining edible crude vegetable oil is provided, wherein the alkali refining comprises the steps of alkali treatment, water washing, drying and the like, wherein the step of alkali treatment is performed by using the method for alkali treatment, the edible crude vegetable oil is crude oil raw material with low phospholipid content, preferably corn crude oil or sunflower seed crude oil, and a separate acidification step is not required before the step of alkali treatment.

In another embodiment of the invention, a method for refining edible crude vegetable oil is provided, wherein the refining comprises a station for alkali refining the edible crude vegetable oil according to the alkali refining method, and a station for decoloring, dewaxing and deodorizing after the alkali refining station.

Advantageous effects

The hypergravity technology has wide applicability, has the advantages of more excellent volume, light weight, low energy consumption, easy operation, easy maintenance, safety, reliability, flexibility, strong environmental adaptability and the like compared with the traditional equipment, and can pertinently solve the problems of large occupied area, heavy weight, high energy consumption, long semi-continuous treatment time and the like of the edible crude vegetable oil deacidification equipment. Meanwhile, the invention can bring the following additional effects:

(1) the retention rate of nutrient substances is higher

In edible crude vegetable oil represented by corn crude oil, tocopherol and phytosterol are two important nutrients. Because both of them contain phenolic hydroxyl group, the grease is easy to react and denature with strong alkali when being in alkaline environment for a long time. The reaction time of the supergravity alkali refining is very short (continuous reaction) compared with the conventional alkali refining, so that the loss of the sterol and the tocopherol is reduced. On the other hand, the alkali refining process is a typical colloid chemical reaction, and in the process, the soap film can adsorb impurities such as colloid and the like and attract each other to be coagulated into a micelle with the time. Under the process of the super-gravity alkali refining, the extremely short reaction time also ensures that the micelle is less formed, and can effectively reduce the adsorption of the sterol and the tocopherol.

(2) Reduce the acid reversion probability

The color reversion of the oil refers to the phenomenon that the color of the edible oil changes from light to dark after filling, transportation and long-term storage, and the acid reversion refers to the phenomenon that the acid value of the edible oil is increased. Present research indicates that grease oxidation is an important factor in causing color reversion. Under the process of the super-gravity alkali refining, the extremely short reaction time can effectively reduce the oxidation of the grease in the high-temperature reaction process, thereby reducing the color reversion degree. The research results show that when the soap content, the metal ion content and the acid value in finished oil are lower, the acid returning degree of the grease is relatively lower, and compared with the traditional alkali refining, the supergravity alkali refining has high reaction efficiency and quick reaction time, and can effectively reduce the soap content, the acid value and the like in the grease, thereby effectively reducing the acid returning degree.

(3) Aiming at processing high-phospholipid and difficult-to-refine oil

In general, the oil and fat which are difficult to refine (mainly the condition that the content of the non-hydrated phospholipid is relatively high) are difficult to remove due to low reaction efficiency of the non-hydrated phospholipid in the traditional alkali refining process, so the alkali refining effect is poor. The non-hydrated phospholipids mainly comprise beta-phospholipids and phospholipid metal complexes such as calcium/magnesium/iron, and the compounds can be removed by reacting with alkali after being acidified. The supergravity alkali refining has high mass transfer rate, and can effectively add the reaction rate of strong base and phospholipid so as to attain the goal of removing phospholipid with high efficiency.

(4) Efficient processing of high acid value oils

In the process of alkali refining and deacidification, the reaction of free fatty acid and strong alkali belongs to a main reaction. Because the acid-base reaction belongs to a fast reaction, the mass transfer rate of the system is high in the process of the hypergravity alkali refining, and the free fatty acid can be removed more fully in the process of the hypergravity alkali refining under the condition of the same alkali amount. Compared with the traditional alkali refining, the neutralized oil acid value obtained by the super-gravity alkali refining is lower, so that the technology is applied to the processing of high-acid-value grease, and the acid value of the neutralized oil can be more efficiently reduced.

Drawings

Fig. 1 is a schematic process flow diagram of an embodiment of the present invention, which is used for alkali treatment and alkali refining of crude oil by a supergravity technology.

FIG. 2 is a schematic process flow diagram of another embodiment of the present invention, which is used for alkali treatment and alkali refining of crude oil by a supergravity technique without water washing.

Fig. 3 is a schematic process flow diagram of another embodiment of the present invention, which is used for alkali treatment and alkali refining of crude oil by a supergravity technique without acidification.

Detailed Description

One embodiment of the present invention will be described in detail below (as shown in fig. 1).

In the context of the present invention, the edible crude vegetable oil refers to edible crude vegetable oil prepared from edible vegetable oil or crude vegetable oil, and examples of the edible crude vegetable oil include soybean crude oil, corn crude oil, sunflower seed crude oil, rapeseed crude oil, and peanut crude oil.

In the context of the present invention, "crude oil" generally refers to unrefined vegetable oil obtained by pressing, leaching or hydrorefining. In the embodiment of the present invention, the crude oil is mainly prepared by the preparation conditions and preparation processes conventional in the art, for example, by the following procedure. The raw materials are pretreated by the steps of peeling, cleaning, crushing, softening (or steaming and frying) and rolling. The oil in the oilseeds is then mechanically pressed out at high temperature and pressure in a press shop. And (3) putting the blank from the blank rolling machine into a steaming and frying pan, steaming and frying, putting the hot blank into a mechanical squeezer, extruding and flowing out the squeezed oil through a squeezing cage gap, removing dregs and impurities through a screening tank and a filter or a filter press, and storing the filtered crude oil. Or crude oil is obtained by solvent leaching after pretreatment and is carried out in a leaching workshop. The mat enters an extractor where it is leached by n-hexane and then enters a series of evaporation devices, usually a series of evaporators, to separate the oil and recover the solvent. The oil from the leaching plant is typically dried in a grease drying tower, after which the crude oil is stored under cooling. The acid value range of the crude oil is 1.40-8.50mg KOH/g, and the content range of the phospholipid is 60-530 ppm.

The "supergravity technology" is a new type of reaction strengthening technology, which can ensure the quick and sufficient contact between crude oil and alkali liquor, as mentioned above, to remove free fatty acid in a very short time.

"alkaline treatment" generally refers to a refining process in which free fatty acids in fats and oils are neutralized with alkali, forming soaps and adsorbing other impurities for removal from the oil. In an embodiment of the invention, the alkaline treatment step is performed in a hypergravity environment. The high-gravity reactor for generating the high-gravity environment can be a rotary packed bed, a stator-rotor reactor and the like, and can also be a vertical reactor or a horizontal reactor. The alkaline treatment step of the present invention is preferably carried out in a continuous feed and discharge manner, with an extremely short actual contact time of the oil phase with the aqueous phase (estimated at 10)^-4On the order of seconds). According to the inventionIt is well documented that similar effects of the invention can be achieved by batch reactions in a hypergravity environment, in addition to hypergravity alkali addition treatment in a continuous manner, as can be readily understood by those skilled in the art.

In a preferred embodiment of the invention, the alkali treatment is carried out at a temperature in the range of 55 to 95 deg.C, preferably 65 to 75 deg.C. If the temperature of the alkali treatment is lower than 55 ℃, the materials are easy to emulsify, the loss of the neutralized oil is excessive, and the alkali treatment effect is poor; if the temperature of the alkali treatment is higher than 95 ℃, the improvement on the whole effect is not obvious, and the energy consumption is too high.

In a preferred embodiment of the invention, the alkaline treatment is carried out at a hypergravity level in the range of 27 to 171g, preferably 62 to 110g (where g is a unit acceleration of gravity known in the art, about 9.8m/s²). If the hypergravity level of the alkali treatment is lower than 27g, the acid value of the neutralized oil and the content of phospholipid are higher, and the alkali treatment effect is poor; if the hypergravity level of the alkali treatment is higher than 171g, the material is easily emulsified, resulting in excessive loss of the neutralized oil and causing excessive energy consumption.

In the embodiment of the present invention, the method further comprises a step of acidifying the crude oil with phosphoric acid before the alkali treatment, wherein the amount of phosphoric acid is converted according to the formula provided in the following examples. In a preferred embodiment of the invention, the excess acid added in the acidification step is between 0 and 40%, preferably between 10 and 20%. If the excess acid is less than 0, the phosphorus content of the neutralized oil is high, and the alkali addition treatment effect is poor; if the excess acid is higher than 40%, the improvement of the overall effect is not significant, and excessive material consumption is caused.

In the embodiment of the present invention, the amount of the base used in the alkali addition treatment is converted according to the formula provided in the following example. In a preferred embodiment of the invention, the excess base in the step of alkali addition treatment is between-5% and 25%, preferably between 5% and 15%. If the excess alkali is less than-5%, the acid value and phosphorus content of the neutralized oil are high, and the alkali addition treatment effect is poor; if the excess alkali is more than 25%, the improvement of the overall effect is not obvious, but the material consumption is too high.

In another embodiment of the present invention, there is also provided an alkali refining process (as shown in FIG. 2) which does not require a separate water washing step after the alkali addition treatment step. The alkali refining process is preferably carried out using a dilute alkali solution, particularly preferably a dilute alkali solution of 6 to 9 baume. When the dilute alkali solution with 6-9 Baume degrees is adopted, the alkali solution is lower than the oil phase, the mixing difficulty is small, and the problems of low reaction rate and long reaction time of the dilute alkali solution can be solved by the supergravity technology; meanwhile, as the water content of the dilute alkali solution is higher, in the separation process, the soap generated by neutralization is soluble in the water phase, so that the soap is taken away from the oil phase, and the obtained product can meet the internal control index of the neutralized oil.

In another embodiment of the present invention, there is also provided a caustic refining process without a separate acidification step prior to the caustic addition treatment step (as shown in FIG. 3). The alkali refining method is suitable for crude oil with low phospholipid content, such as crude oil of corn and sunflower seed oil, and is especially suitable for crude oil with high acid value (such as 4.0-12.0mgKOH/g), low phosphorus content (such as 80-240ppm), and low non-hydrated phospholipid content (such as 20-80 ppm). The addition amount of the alkali liquor calculated according to the formula is higher, so that the phase ratio of the water phase to the oil phase is lower, and the mixing effect is better; because the acid value of the raw material is higher, more soap is generated, so that the phospholipid in the crude oil can be removed by adsorption; meanwhile, part of the alkali liquor can also react with the phospholipid, so that efficient removal is realized. The alkali refining method can obtain a product meeting the internal control index of the neutralized oil without front-end acidification.

In the embodiments shown in fig. 2 and 3, the selection and control of the raw materials and process parameters can be performed in the same manner as in the embodiment shown in fig. 1.

Examples

The following materials and equipment were used in the examples of the present invention. It will be understood by those skilled in the art that the scope of the present invention is not specifically limited by the following parameters and steps.

The crude soybean oil and the crude corn oil adopted in the embodiment of the invention are prepared according to the method described above, wherein the acid value of the crude soybean oil is 2.60mgKOH/g, and the phosphorus content is 430 ppm; the crude corn oil has an acid value of 5.81mgKOH/g and a phosphorus content of 112 ppm.

The supergravity devices employed in the embodiments of the present invention are all devices already disclosed in the earlier patents (application numbers 91111028.3, 91109255.2, 01268009.5, 200520100685.3, 02114174.6, 200510032296.6, 201610515008.0, 201910053047.7, 201910711393.X) as described above.

Example 1

The present embodiment is performed by the following steps:

step 1: acidification

Weighing 200g of crude oil, and calculating the mass of added phosphoric acid according to the following formula:

wherein M is the weight (kg) of the crude oil, P is the content (ppm) of the non-hydrated phospholipid, x is the excess acid (%), and C is the concentration (%) of the phosphoric acid.

The acidification step was completed by adding acid at 75 ℃ and stirring at 1000rpm for 40 min. And simultaneously, the corresponding optimization is carried out by taking the initial condition as the initial condition.

Step 2: alkali treatment

The mass of the added NaOH solution was calculated as follows:

wherein M is the weight (kg) of the crude oil, A is the acid value (mg KOH/g) of the crude oil, y is excess base (%), and C is the concentration (%) of NaOH.

The alkaline treatment step of each example was carried out in a continuous feed and discharge manner using the supergravity apparatus described above. The actual contact time of the oil phase and the water phase is very short, and the initial estimation is 10^-4On the order of seconds.

And step 3: washing with water

Directly collecting the product treated by adding alkali at the outlet of the supergravity equipment, washing the oil phase obtained after centrifugation with water (adding water or citric acid (mass fraction of 0.25%) solution with the weight of the oil being 8%, stirring at 300rpm at 92 deg.C for 10min), centrifuging, and collecting the oil phase.

And 4, step 4: drying

Drying the oil phase product after water washing at 80 ℃, and conveying the neutralized oil to a storage tank for storage after the temperature is reduced to 40-60 ℃. The quality of the prepared neutralized oil is qualified when the phosphorus content is less than 10ppm and the acid value is less than 0.2 mg/g.

The specific process operating parameters are as follows: 20% of excess acid(s), 10% of excess alkali (a), 6 baume of alkali concentration (c), 75 ℃ of alkali refining temperature (T), 110G of hypergravity level (G) and 8% of oil weight of water are washed, and the soybean crude oil with acid value of 2.60mg KOH/G and phosphorus content of 430ppm is subjected to alkali treatment. The resulting final product had an acid value (v) of 0.02mg KOH/g, a phosphorus content (P) of 2.97ppm, a relative sterol retention (m, compared to conventional caustic refining under the same reaction conditions) of 104%, and a relative alpha-tocopherol retention (n, compared to conventional caustic refining under the same reaction conditions) of 109%. The obtained neutralized oil is decolorized (dewaxed) and deodorized, and then is subjected to eighteen-month shelf life experiments, so that the phenomenon of acid reversion and color reversion is not generated.

Examples 2 to 15:

the test procedure is the same as that of example 1, the specific process parameters and test results are shown in the following table 1, the parameters not listed in the table are the same as those of example 1, and the meanings and units of the letters listed in the head of the table are completely the same as those of example 1:

TABLE 1

Example 16: effect of omitting the Water washing step on the final product

Keeping other conditions unchanged (the hypergravity level is 62g, the alkali concentration is 6 Baume degrees, the excess acid is 20 percent, the excess alkali is 10 percent, the alkali refining temperature is 75 ℃), and performing an acidification step on the soybean crude oil with the acid value of 2.60mg KOH/g and the phosphorus content of 430ppm in a manner of omitting a water washing step. The parameters of the final product obtained are shown in table 2.

TABLE 2

	Acid value mg KOH/g	Phosphorus content ppm
			Experimental group 1	0.07	6.21
Experimental group 2	0.05	5.82
			Experimental group 3	0.05	6.33

Example 17: effect of omitting the acidification step on the final product

Keeping other conditions unchanged (110 g of hypergravity level, 6 Baume of alkali concentration, 20% of excessive alkali, 75 ℃ of alkali refining temperature and washing with water by using citric acid aqueous solution with the mass fraction of 0.25% of oil weight of 8%), and carrying out an acidification step on the corn crude oil with the acid value of 5.81mg KOH/g and the phosphorus content of 112ppm in a mode of omitting the acidification step. The parameters of the final product obtained are shown in table 3.

TABLE 3

	Acid value mgKOH/g	Phosphorus content ppm
			Experimental group 1	0.07	4.55
Experimental group 2	0.06	4.62
			Experimental group 3	0.05	5.21

From the results of the above examples, it can be seen that the method of the present invention, which is used to perform alkali refining deacidification of crude oil within the process operation parameters claimed by the present invention, can obtain high quality oil products with low acid value, low phosphorus content and high nutrient retention rate. And the above embodiments are all carried out under the condition of continuous production, and the production efficiency is greatly improved.

Claims

1. A method for carrying out alkali treatment on edible crude vegetable oil is characterized in that the alkali treatment is carried out by a supergravity technology; preferably, the alkali addition treatment is carried out as a continuous reaction.

2. The method of any one of the preceding claims, wherein the alkali addition treatment is performed at a hypergravity level of 27-171g, preferably 62-110 g.

3. The process of any one of the preceding claims, wherein the alkalifying treatment is performed with 6-15 baume NaOH.

4. A process according to any one of the preceding claims, wherein the alkali treatment is carried out at a temperature of 55-95 ℃, preferably 65-75 ℃.

5. The process of any one of the preceding claims, wherein the alkali treatment is carried out with an excess of alkali of-5% to 25%, preferably 5% -15%.

6. The method according to any one of the preceding claims, wherein the edible raw vegetable oil is selected from one or more of the group consisting of soybean raw oil, rapeseed raw oil, peanut raw oil, corn raw oil, sunflower seed raw oil.

7. A method for alkali refining edible crude vegetable oil comprises the following steps:

(1) acidifying: adding phosphoric acid into raw vegetable oil as a raw material under a heating condition, and stirring; preferably, the acidification step is carried out with an excess of acid of 0-40%, preferably 10-20%;

(2) alkali treatment: performing an alkali addition treatment by the method of any one of claims 1 to 6;

(3) and (3) water washing: washing the product after alkali treatment with water or citric acid solution;

(4) and (3) drying: and drying the product after washing.

8. A method for alkali refining edible crude vegetable oil comprises the following steps:

(2) alkali treatment: performing an alkalization treatment using the method of any one of claims 1 to 6, preferably the alkalization treatment is performed using 6 to 9 baume degree NaOH;

(3) and (3) drying: drying the product after alkali treatment;

wherein a separate water washing step is not required after the alkali addition treatment step.

9. A method for alkali refining edible crude vegetable oil comprises the following steps:

(1) alkali treatment: performing an alkali addition treatment by the method of any one of claims 1 to 6;

(2) and (3) water washing: washing the product after alkali treatment with water or citric acid solution;

(3) and (3) drying: drying the product after washing;

wherein the edible plant crude oil is a crude oil raw material with low phospholipid content, preferably crude corn oil or crude sunflower seed oil; and no separate acidification step is required prior to the alkali addition treatment step.

10. A method for refining crude edible vegetable oil, said refining comprising a stage of caustic refining said crude edible vegetable oil according to the method of any one of claims 7 to 9, and a stage of decoloring, dewaxing and deodorizing after said caustic refining stage.