RU2505593C1 - Method of purifying vegetable oil - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves cooling oil, adding an activated crystallisation initiator, holding while mixing phases and separating impurities with a filter. The activated crystallisation initiator used is refined wooden filter material. Said material consists of not more than 75% cellulose and not more than 25% lignin and is added in amount of 0.3-1.2% of the mass of oil. When adding, the amount of said material is divided into two portions: 1/3 and 2/3 or 1/4 and 3/4 of the total volume. The first portion of the material and oil at temperature 35-45°C are first fed into a first crystalliser. The obtained suspension at temperature of 20-25°C is then fed into a second crystalliser and then cooled by a coolant to temperature of 10°C for 1.5-2.5 hours while stirring continuously. The suspension cooled to temperature of 10°C is then fed into a third crystalliser and then cooled by a coolant to temperature of 0-4°C for 1.5-2.5 hours while stirring continuously. The suspension cooled to temperature of 0-4°C is then fed into a first holding container and held for 2.5-3.5 hours at temperature of 0-4°C. The suspension at temperature of 0-4°C and the second portion of the refined wooden filter material are fed into a second holding container and held at temperature of 0-4°C. The obtained suspension is heated to temperature of 15-20°C. Mixing in crystallisers is carried out at a rate of not more than 3-7 rpm.

EFFECT: invention reduces the time for cleaning oil and increases efficiency of cleaning.

8 cl

Description

The invention relates to the oil industry and can be used to clean vegetable oil from waxes.

A method for purifying vegetable oil has been developed and tested within the framework of the Bio-Control internal quality control system adopted by Kazan Fat Plant OJSC.

A known method of purification of vegetable oil (RF patent No. 2224787, IPC С11В 3/00, СВВ 3/10, publ. 02/27/2004), comprising cooling the oil, introducing an adsorbent into it with stirring and filtering, the second sunflower meal is used as an adsorbent pressing in an amount of 0.1-0.2% by weight of oil or flour of grape seeds in an amount of 0.2 0-4% by weight of oil.

A known method of purification of vegetable oil (RF patent No. 2117034, IPC C11B 3/00, C11B 3/16, publ. 08/10/1998), including filtering and subsequent separation of the precipitate, before filtering the oil, add a reture (return) filter cake in the ratio 20: 1, at the same time mix and cool the oil to 15-20 ° C, and then direct it to the battery of horizontal settling tanks of periodic action.

A known method of cleaning vegetable oils from waxes (RF patent No. 2317322, IPC СВВ 3/00, СВВ 3/10, publ. 02.20.2008), the closest in technical essence and adopted as a prototype, including cooling the oil to 12-13 ° C, introducing an activated crystallization initiator into it, holding the phases under stirring and separating impurities on a vacuum filter, use the kaolinite-r-quartz mineral mixture in the ratio 9: 1 ÷ 9.8: 0.2 treated as grinding with sodium percarbonate at a ratio of 8: 1 ÷ 42: 1, subsequent spraying on the surface of the product of grinding a solution of phosphoric acid with a concentration of 20-25%, taken in an amount of 50-75% by weight of the mixture, and drying, while the crystallization initiator is introduced into the oil in relation to impurity waxes of 1: 1 ÷ 2: 1 in an amount not less than 0.1% by weight of the oil, and the exposure is carried out for 4-5 hours while stirring the phases with an intensity of 0.5-1.0 s ^-1 .

The objective of the invention is to develop a method for the purification of vegetable oils from waxes by introducing a natural crystallization initiator — refined wood filtering material (DRFM), which ensures the removal of wax-like substances, reducing energy consumption.

To achieve the above objective, OJSC Kazan Fat Factory, within the framework of the Bio-Control internal quality control system, developed a method for purifying vegetable oil by introducing an environmentally friendly, natural crystallization initiator - DRFM.

The technical result of the invention is to reduce the time of the oil purification process by introducing a natural crystallization initiator, and to increase the oil purification efficiency.

The technical result is achieved in that in a method for purifying vegetable oil, including cooling the oil, introducing an activated crystallization initiator into it, holding the phases under agitation and separating impurities using a filter, it is new that a refined wood filter material is used as the activated crystallization initiator, consisting of cellulose not more than 75% and lignin not less than 25%, in an amount of 0.3-1.2% by weight of oil, which is divided into two parts: 1/3 and 2/3 or 1/4 and 3/4 of total volume

aging with stirring of the phases is carried out by a sequence of steps in which:

the first part of the refined wood filtering material is fed into the first crystallizer and the oil cooled to a temperature of 35 ° -45 ° C, the resulting suspension is cooled with a refrigerant to a temperature of 20-25 ° C for 1.5-2.5 hours with continuous stirring;

fed to the second crystallizer the resulting suspension with a temperature of 20-25 ° C, cooled it with a refrigerant to a temperature of 10 ° C for 1.5-2.5 hours with continuous stirring;

a suspension cooled to a temperature of 10 ° C is fed to a third crystallizer, then it is cooled with a refrigerant to a temperature of 0-4 ° C for 1.5-2.5 hours with continuous stirring;

served in a first holding tank cooled to a temperature of 0-4 ° C suspension and incubated for 2.5-3.5 hours at a temperature of 0-4 ° C;

served in a second container for aging suspension with a temperature of 0-4 ° C and the second part of the wood refined filter material and kept at a temperature of 0-4 ° C;

then the resulting suspension is heated to a temperature of 15 ° -20 ° C,

moreover, mixing in the crystallizers is carried out at a speed of not more than 3-7 rpm

The oil is pre-hydrated, bleached at a temperature of 85 ° -105 ° C.

The oil is cooled in heat recovery heat exchangers due to heat exchange with cold winterized oil to a temperature of 35-45 ° C.

Propylene glycol with a temperature of minus 3 ° C is used as a refrigerant in the crystallizer.

1/3 or 1/4 is supplied to the first crystallizer, and 2/3 or 3/4 of the total estimated amount of wood refined filter material is supplied to the second holding tank.

The total residence time of the suspension in the first and second crystallizers is not more than 3.0-5.0 hours.

From a suspension heated to 15 ° -20 ° C, the impurities are separated using a filter under a pressure of 0.25 to 0.5 MPa to obtain a winterized oil.

The winterized oil is fed to the deodorization stage.

Before starting the winterization process, the oil must first be neutralized and bleached. The bleaching stage takes place at a temperature of 85 ° -105 ° C.

To obtain high-quality vegetable oils, they must be maximally cleaned of related substances, i.e. mechanical impurities, phosphatides, wax-like substances.

Wax substances are mixtures with a predominant content of esters of high molecular fatty acids and monoatomic (less often diatomic) alcohols, carotenoid alcohols of nature (colored waxes). The wax fraction of lipids also includes free high molecular weight fatty acids and alcohols, as well as sterols, sterids, hydrocarbons, lactones and estolides. Wax substances in the process of extracting the oil pass from the seed, where their content ranges from 0.01 to 0.3%. The presence of waxy substances in the oil mainly determines the degree of its transparency. Due to the high melting point (32-98 ° C), wax substances form a thin and very stable suspension of crystals in the oil when it is cooled, the so-called net, which significantly worsens the presentation of the oil. None of the stages of oil refining (hydration, alkaline neutralization, bleaching, deodorization) practically leads to the removal of wax substances. In this regard, their presence in oil not only does not allow to obtain oil with a good presentation, but also causes difficulties in processing.

The process of winterization consists in slowly cooling the oil and holding it at a low positive temperature, followed by separation of the precipitate by filtration. To increase the productivity of the line, the process is carried out using a filter powder (FP). FP particles act as centers of wax crystallization, and also provide drainage properties of the precipitate.

The objective of the invention is solved in that as a filter powder use wood refined filter material (DFID) in an amount of 0.3-1.2% by weight of oil.

DRFM consists of cellulose (not more than 75%) and lignin (not less than 25%).

Cellulose is one of the most common biopolymers that make up the cell walls of plants and microorganisms.

Cellulose - a white fibrous substance is a long strand of more than 20 mm, containing 300-10000 glucose residues, without side branches. These threads are interconnected by many hydrogen bonds, which gives the cellulose mechanical strength.

Cellulose forms the crystalline skeleton of the cell membrane.

Of great importance in the proposed DRFM is lignin, which has amorphous properties, fills the space in the cellulose crystal lattice and enhances the strength of the cell membrane, thereby providing high drainage properties of the DRFM.

The high adsorption capacity of DRFM, on the one hand, is due to the developed capillary-porous structure of cellulose, including: intra-fibrous packaging irregularities (size 1.5 nm); interfibrial pores (1.5-10 nm); pores arising as a result of internal stresses (several tens of nm); channels and pores with a diameter of several microns, on the other hand, revealed high drainage properties due to the presence of lignin in the structure of cellulose fibers.

Durable DRFM structure with high drainage properties:

- has a positive effect on the stability of the filter cake. DRFM particles are less destroyed during transport, and create an incompressible filter layer. It is much less susceptible to compression with increasing pressure.

- allows you to withstand a larger number of regeneration cycles compared with other FP, which leads to a significant reduction in the cost of the process.

- leads to a significant increase in filter time. Due to the lower bulk density, there is no restriction on the weight of the filter powder, the maximum permissible per unit surface area of the filter.

It has been experimentally proved that the presence of lignin in the DRFM of at least 25% provides the claimed technical result.

The method is as follows.

The pre-hydrated (neutralized) bleached oil with a temperature of 85-105 ° C enters the stage of winterization by means of a feed pump to the winterization workshop, where it is pre-cooled in several heat recovery heat exchangers by heat exchange with cold winterized oil that has already passed the stage of winterization, to a temperature of 35-45 ° C.

To ensure the entire process of winterization, three crystallizers are needed, two holding tanks (matutator), a heater and a filter.

Crystallizers are containers with a mixing device and a cooler in the form of a coil, into which a refrigerant (refrigerant) is supplied. Propylene glycol with a temperature of minus 3 ° С, water or another liquid is used as a refrigerant.

Holding tanks (maturators) also contain coils, inside which refrigerant is also supplied.

Sealed strainer should have filter elements (cells), the size of which is smaller than the size of large crystals of wax in a suspension of oil-DRFM.

Pre-cooled to 35 ° -45 ° C, the oil is fed into the first crystallizer, which also serves a predetermined amount of DFID from the feed system.

The amount of DRFM depends on the wax content in the starting oil, i.e. from the type of oil itself and calculated from the total volume of oil, divide this amount into equal parts, from which serves:

- 1/3 or 1/4 of the calculated amount in the first mold;

- 2/3 or 3/4 of the calculated amount in the second holding tank.

With continuous stirring at a speed of 3-7 rpm oil

mixes with DRFM, resulting in a suspension of oil-DRFM, in which the first wax crystals begin to form, settling on particles of DRFM.

A refrigerant circulates through the coil of the first crystallizer, using propylene glycol with a temperature of minus 3 ° C. Propylene glycol is cooled in a refrigerator using cold water at a temperature of 20-25 ° C.

The refrigerant passing through the coil cools the suspension of oil-DRFM to a temperature of 20-25 ° C for 1.5-2.5 hours.

Then cooled to 20-25 ° C, a suspension of oil-DRFM enters the second mold.

In the second crystallizer, the oil-DRPM suspension is cooled to a temperature of 10 ° C with a refrigerant, which also uses propylene glycol with a temperature of minus 3 ° C for 1.5-2.5 hours, with slow stirring at a speed of 3-7 rpm.

This leads to the further formation of wax crystals on the developed surface of DRFM particles.

In the second mold, a certain temperature difference can be maintained between the refrigerant and the oil in order to avoid blast chilling.

An important requirement of the winterization process is the slow cooling rate. For proper crystal formation, the temperature should decrease from 35-45 ° C to 0-4 ° C in 5-8 hours. A high cooling rate leads to the formation of a large number of very small crystals, as well as a high rate of nucleation of crystallization centers, resulting in an increase in the viscosity of the oil, which, in turn, limits the growth of crystals and slows down the filtration process.

Small crystals can clog the filter, which will make the filtration process more difficult, and will also lead to overspending of the filtered powder (DRFM).

Mixing accelerates the formation of wax crystals due to more active contact of the crystals with the liquid phase. However, it is necessary to apply moderate mixing speeds, not more than 3-7 rpm, since high mixing speeds lead to the destruction of wax crystals during the growth phase and the formation of smaller fragments instead of the necessary large solid particles.

The crystallization temperature also affects the growth rate of wax crystals. The high viscosity of the oil, observed at too low a temperature below 0 ° C, reduces the crystal growth rate. Temperature control after crystallization begins is very important for the transition from the α-form of crystals to a stable β′- or β-form. In the absence of proper control of the parameters (mixing speed and cooling rate) of the process, unstable crystals will form at this stage.

From the second crystallizer, the oil-DRPM suspension cooled to 10 ° C enters the third crystallizer, where the final cooling of the oil-DRPM suspension to a temperature of 0-4 ° C takes place within 1.5-2.5 hours.

The total duration of the suspension of oil-DRFM in three crystallizers is 5.0-8.0 hours.

Then the suspension of oil-DRFM at a temperature of 0-4 ° C enters the first holding tank, in which the suspension is further aged for the final maturation of wax crystals.

The maximum residence time of the suspension in the first container for holding 2.5-3.5 hours at a temperature in the range of 0-4 ° C.

From the first holding tank, the thickened suspension of oil-DRFM with a temperature of 0-4 ° C with ripened wax crystals is fed into the second holding tank, where the rest is fed at the same time - 2/3 or 3/4 of the calculated amount of DRFM to improve the filtration process.

The maximum residence time of the suspension in the second container for holding 2.5-3.5 hours at a temperature in the range of 0-4 ° C.

From the second holding vessel, the suspension first passes through a preheater in which it is heated to 15 ° -20 ° C (predominantly 18 ° C) to reduce viscosity and improve the filtration process.

If the temperature rises above 20 ° C, a reverse transition of wax crystals to oil may begin.

Further, the suspension heated to 15 ° -20 ° C enters the filtration, i.e. in soft mode, it is pumped to a pre-washed sealed strainer.

The thickness of the suspension should be such that it passes through the filter cells only under pressure. Depending on the type of filters, the filtration pressure can be from 0.25 to 0.5 MPa.

Passing through the filter, large wax crystals together with particles of DRFM are separated from the oil and remain on the filter elements.

Large fragments of waxes are needed for better filtration. Fine fractions “clog” the filter, which can lead to an increase in the duration of the winterization process.

The winterized oil that has passed through the filter goes to the deodorization stage.

The process control is fully automated.

All technological processes are measured by a system of instruments with the transfer of results to a programmable controller for summation and accounting.

Any changes in the oil flow are measured and recorded, which automatically adjusts the dosage level of additives in the filter. The automatic control system provides the set temperature in the crystallization tanks, cooler and oil heater.

The main advantages of refined wood filtering material (DRFM) are its low bulk density, low thermal conductivity, chemical inertness, sterility, fire resistance, good sound insulation properties, etc.

A particle with the necessary geometrical dimensions, capable of providing the subsequent filtration process with specified filter performance parameters, can act as a crystallization center.

It is important to understand that dosing occurs in bulk parts. And in fact, only the number of particles per unit volume that can crystallize the amount of wax that was contained in the original oil matters. How much a particle will weigh - in this case, it is neither important nor critical.

The bulk density of the DRFM is lower than that of other filter powders (for example, kieselguhr), but the particle size is the same, therefore, the same number of particles will be contained in the same volumes, but the weight of the DRFM introduced into the process will be half as much. Therefore, with the same volumetric flow rate of the FP, the mass flow rate of the DFGM will be less than the flow rate of other phase transitions (for example, kieselguhr).

Due to the fact that when replacing filter powders with DRFM, less FP by weight is involved in the process, oil losses are sharply reduced.

The average value of the residual oil content of cake on the filter in the industry is 50-55%. The specific value of the residual oil content of the cake depends, first of all, on the quality indicators of the initial oil, installed equipment, air pressure in the system, and filter purge time.

Advantages of DRFM over other filter powders:

- safety for health;

- high purity;

- lack of abrasiveness;

- can be removed seamlessly and without pollution;

- in comparison with mineral filtering agents, they provide optimized flow rate and improved environmental balance;

- amorphous material, without crystalline and needle-like debris;

- cost savings on the purchase of powder;

- particle size distribution, providing a long filtering period with high performance;

- stable filtering process;

- high speed filtration;

- high degree of oil purification from waxes;

- low oil absorption of spent filter powder;

- reduction of oil losses with spent powder;

- reducing the cost of disposal of spent filter powder;

- depending on the length of the fibers have a consistent permeability;

The tasks are also achieved by:

- automatic control of the main process parameters, in particular, the degree of cooling and crystallization with the help of a programmable controller, which ensures constant product quality;

- ensuring volumetric and uniform crystal growth at a certain ratio of oil temperature and cooling agent;

- the design of a system for efficient separation of waxes;

- the presence of a filter of a special design that feeds the pump, which avoids the destruction of crystals;

 ease of operation and maintenance.

Wood refined filter material can be obtained by the method of producing wood refined filter material according to the application No. 20111144935 from 03.11.2011

The test results and the chemical-physical analysis of the purified product, obtained in accordance with the approved industry methods, as well as the methods adopted at Kazan Fat Factory, confirm the conformity of the developed method to the stated technical result.

Claims (8)

1. A method of purifying vegetable oil, including cooling the oil, introducing an activated crystallization initiator into it, holding the phases under agitation, and separating impurities using a filter, characterized in that the wood refined filter material consisting of cellulose no more than 75 is used as the activated crystallization initiator % and lignin not less than 25%, in an amount of 0.3-1.2% by weight of the oil, which is divided into two parts: 1/3 and 2/3 or 1/4 and 3/4 of the total volume,
aging with stirring of the phases is carried out by a sequence of steps in which:
the first part of the wood refined filter material is fed into the first crystallizer and the oil cooled to a temperature of 35-45 ° C, the resulting suspension is cooled with a refrigerant to a temperature of 20-25 ° C for 1.5-2.5 hours with continuous stirring;
feeding the suspension obtained at a temperature of 20-25 ° C into the second crystallizer, cooling it with a refrigerant to a temperature of 10 ° C for 1.5-2.5 hours with continuous stirring;
a suspension cooled to a temperature of 10 ° C is fed to a third crystallizer, then it is cooled with a refrigerant to a temperature of 0-4 ° C for 1.5-2.5 hours with continuous stirring;
served in the first holding tank cooled to a temperature of 0-4 ° C suspension and incubated for 2.5-3.5 hours at a temperature of 0-4 ° C;
served in a second container for aging suspension with a temperature of 0-4 ° C and the second part of the wood refined filter material and kept at a temperature of 0-4 ° C;
Further, the resulting suspension is heated to a temperature of 15-20 ° C, and mixing in the crystallizers is carried out at a speed of not more than 3-7 rpm. 2. The method according to claim 1, characterized in that the oil is pre-hydrated, bleached at a temperature of 85-105 ° C. 3. The method according to claim 1, characterized in that the cooling of the oil occurs in heat recovery heat exchangers due to heat exchange with cold winterized oil to a temperature of 35-45 ° C. 4. The method according to claim 1, characterized in that propylene glycol with a temperature of minus 3 ° C is used as a refrigerant in the crystallizer. 5. The method according to claim 1, characterized in that 1/3 or 1/4 is supplied to the first crystallizer, and 2/3 or 3/4 of the total estimated amount of wood refined filter material is supplied to the second holding tank. 6. The method according to claim 1, characterized in that the total residence time of the suspension in the first and second crystallizers is not more than 3.0-5.0 hours 7. The method according to claim 1, characterized in that from the suspension heated to 15-20 ° C, the impurities are separated using a filter under a pressure of 0.25 to 0.5 MPa to obtain a winterized oil. 8. The method according to claim 7, characterized in that the winterized oil is fed to the deodorization stage.