US2236493A - Process of refining corn oil - Google Patents

Description

March 25, 1941. G, A, MOORE PRCESS 0F REFINING CORN OIL Filed June 3, '1938 Ilnll' l'mfen or Patented Mar. 25, 1941l PRocEss F REFiNmG CORN oIL George A. Moore, Oak Park, lll., assignor, by mesne assignments, to Corn Products Refining Company, New'York, N..Y., a corporation of New Jersey Application June 3, 1938, Serial No. 211,593

, 3 Claims. (Cl. 26o-425) This invention relates to the refining of vegetable oils, more particularly corn (maize) oil.

It has been customary to refine corn oil by a processsubstantially as follows: The crude oil is 5 lintroduced into a tank or kettle provided with steam coils' and an agitator. A water solution of caustic soda-is mixed with `the oil in the kettle,

. by-means ofthe agitator, and the mixture is heated ata temperature of 110 F. for about 0 four 4hours, during which time the break socalled,occurs. 'The agitator is then stopped and A.the soap stock bodies produced by the neutralization of the fatty acids and other impurities in the oil through the action of the caustic soda are allowed to settle for about eighteen hours. -The settling divides the oil and water emulsion or mixture into an upper stratum of oil which is drawn o and subjected to decolorizing, deodorizing and other treatments which need not be 2 -referred to here, anda lower stratum consisting of soap stock and some oil, which latter may be recovered and reprocessed. 'I'he crude oil subjected to the treatment just outlined contains, in addition to fatty acids, nonfatty acid impurities derived from the corn kernel, namely, pigment coloring matter, such as carotin and chlorophyl, protein, starch, sugar, pentosans. cellulose and steep water solids, such as amino acids and polypeptides. The caustic soda not only reacts with the fatty acids to form soap but also reacts with the non-fatty acid impurities to convert them into water soluble products which are capable of being removed from the oil along with the neutralized fatty acids. The length 0f time required for the mixing step is necessitated more because of the presence in the oil of the'non-fatty acid impurities than by the presence of the fatty acids which latter react very quickly with the alkali. Temperature is also a 40 factor in the refining step, particularly in respect to reaction between the alkaline solution and the non-fatty acid impurities. The reaction. takes place more quickly at -high temperatures, but with the risk of loss of oil by saponication. Hence, the temperature used must be a matter of compromise. The impurities, i. e.,- the saponied fatty acids and non-fatty acids, are collectively spoken of'as soap stock or foots.

It has been proposed at various times to substitute, in the refining of vegetable and other oils,

centrifugal separation of oil from soap stock for separation by gravity; but these processes have proven unsuccessful, in most cases, and at best not entirely satisfactory,at least as applied to the refining of corn oil. The separation has not been as complete as in the kettle process, in rey-spect particularly, perhaps, to the removal o! the .non-fatty acidimpurlties, as evidenced by the .reddish color which is found to remain in the cenfailed to appreciate the principles which must be .taken into account if complete separation, resulting-in ,an Poil of high purity and low color index,y 15 is `to be eifected. Centrifugal separation has obvious advantages, such as saving of time, equipment and floor space; and should, theoretically, at least, give oil of higher quality, as well as better yields.

The primary object of the present invention is to provide a process of refining corn oil, employing the principle of separation of the soap stock from the oil by centrifugal force, which, besides -being more convenient than the old kettle process, will give a purer oil, anv oil of diminished color, and also better yields from the crude oil treated.V The invention, however, does not depart, as has been heretofore attempted, from the fundamental principles of the gravity separation practice,-but rather follows such principles and adapts them to the new technique. To thisv 4adaptation of gravity separation principles to separation by centrifugal force is due, it is believed, the success of the process. 3

The invention is illustrated .in the hereto appended diagrammatic flow-sheet.

Referring to this flow-sheet, A designates a ,crude oil settling tank in which the oil is allowed to settley and the settlings drawn off at l. -B is 40 a tank, provided with heating coil 2 and agitator 3, into which tank the oil drawn from tank A .through pipe 4 is pre-heated to 90-100 F. in order that it may be given suitable fluidity for easy mixing with the caustic soda solution. The 45 oil thus heated at B passes through pipe 5 and the caustic solution through pipe 6 to the mixing or emulsifying apparatus which is here shown as consisting of two mixers D, D', each provided with an agitator 1, or other suitable means for 50 effectively mixing the oil and alkaline solution, the mixing vessels being connected by a pipe 8. Ihe flows through pipes 5 and 6 are controlled by the proportioning meter C to give a proper mixture of oil and caustic. From the mixing ves- 55 sel D' the mixture passes through pipe 9 to a heater E where it is heated to a temperature preferably of 130140 F.

If desired, the mixture may be given the requisite temperature by heating either the oil or caustic solution or both before mixing takes place; but better results appear to be obtained when the oil and alkaline solutions are first mixed and then heated. F is the primary centrifugal machine for eiecting the separation between oil and soap stock. The oil passes through pipe i0 to a washing tank G into which water is introduced through pipe I i at a temperature to raise the mixture to 180 F. The mixture of oil and water passes through pipe i2 to the washing centrifuge H, the oil from which goes through pipe i3 to the vacuum drier J.

The operation, as Just described, provides for the mixing of the oil and caustic soda solution to form an emulsion, at least a very intimate mixture of the crude oil and water solution, as in the case of the kettle process. In the new process the centrifuging takes the place of the gravity separation. In both processes the mixtures are at somewhat elevated temperaturestemperatures favorable to reaction between the alkali and the oil impurities and favorable to bringing about the break in the emulsion or mixture. But there is another important factor which has been to a large extent overlooked. In the kettle process the mixture stands for a long time, some eighteen hours, which not only permits the soap stock particles to subside, but allows the smaller particles to coalesce and form larger particles, which is necessary in order that clarification by subsidence should take place in an effective manner. This period of coalescence is provided for automatically in the gravity settling of the kettle method. But when centrifugal separation is substituted for gravity separation, it has to be provided for specially, otherwise cornplete separation is not attained. To provide for a period of time before centrifuging during which coalescence of the smaller soap stock particles may take place, applicants apparatus does not run the mixture from the heater E directly into the centrifugal machine F, but causes it to pass through a conduit of considerable length, for example, through twenty-five feet of four inch pipe, in the form, preferably, of a loop vertically arranged so as to prevent stratification of the mixture, which, if it occurred would make the action of centrifuging irregular and defective. The pipe K could be arranged horizontally. provided the diameter of the pipe were small enough and the velocity of the flow proportionately great enough to prevent appreciable settling of the soap stock during the flow from the heater E to the centrifuge F. That is the stream is of such diameter and velocity as to preserve the mixture in a homogeneous state when it reaches the centrifugal machine. In the installation shown diagrammatically on the oW-sheet, the time required for the mixture to flow from the mixer D' through the heater is about four minutes. The flow from the heater to the centrifugal machine through the loop requires another four minutes. Under these conditions the temperature to which the mixture is heated is from 130140 F., 140 being about Vas high as it is possible to heat the oil without danger of saponification ot the oil itself. By making the loop longer, the temperature might be lowered somewhat. With the long period for coalescence permitted by the kettle process, it is entirely practical to heat the mixture to only 110 F. But as in the centrigual process, no period between heating and centrifuging can be greatly extended without inconvenience, it is best to use temperatures as high as practical and thus shorten as much as possible the loop K or its equivalent. It is quite possible that more than coalescence of small particles into larger takes place in the loop. The loop also gives scope for reaction between the caustic soda and the non-fatty acid impurities which requires more time than that between the alkali and the fatty acid.

I claim:

1. In the process of refining corn oil in which a mixture is made of the crude oil and an alkaline solution, with the application of heat to give the mixture a breaking temperature, whereupon the mixture is centrifuged to separate foots from the oil: the improvement which consists in prolonging the contact between the alkaline solution and the oil by causing the mixture, after being heated, to flow tothe centrifugal machine through a substantially vertically arranged conduit Whereby settling is prevented, in a homogeneous stream of such length as to allow completion of the reaction between the alkaline solution and the oil impurities and coalescence of the foots, particles, whereby a substantially complete separation of impurities takes place.

2, In the process of rening corn oil which comprises: mixing an alkaline solution with the crude oil; heating the mixture to a breaking temperature; and centrifugng the mixture to separate foots from oil: the improvement which consists in prolonging the contact between the a1- kaline solution and the oil, after the mixture has been effected, by causing the mixture after being heated to flow to the centrifugal machine through a substantially vertically arranged conduit whereby settling is prevented.

3. Process of refining corn oil which comprises: heating the crude corn oil to a temperature of about 90100 F.; mixing an alkaline solution with the oil; heating the mixture to a temperature of about 130-140 F.; causing the heated mixture topass through a substantially vertically arranged rauh-bent conduit at such velocity as to require about four minutes for the material to reach the centrifugal after being heated; and then centrifuging the mixture to separate foots from oil.

GEORGE A. MOORE.

Images