US1828035A - Recovery of oil from spent fuller's earth - Google Patents

Description

Patented Oct. 20, 1931 CARLETON ELLIS, OF MONTGLAIR, NEW JERSEY RECOVERY OF OIL FROM SPENT FULLERS EARTH No Drawing. Application filed February 28, 1923, Serial No. 621,929. Renewed February 14, 1931.

This invention relates to the recovery of oil from fullers earth and similar earths which have been used in bleaching and refining of oils and the like and relates especially 5 to the separation of the oil from the earth by means of aqueous alkaline solutions.

The use of gasoline and other volatile organic solvents for extracting oils from spent earths involves fire hazards. In the present 11 invention it is an object to use aqueous solutions as the extracting medium in order to avoid the use of inflammable solvents.

For the purpose of extraction, an aqueous solution is prepared containing 2 per cent by 15 weight of caustic soda and 10 per cent of common salt. This is brought to a boiling temperature and a quantity of spent fullers earth approximately equalto the weight of the solution is added. Air or steam or both may then be blown through the mixture for purposes of agitation, heat meanwhile being applied to cause slow ebullition. Tl'llS may continue for about 30 minutes then the mixture is allowedto stand for about 15 minutes. Water which has previously been heated to about 150 F. is added to the mixture to dilute the alkaline solution. A quantity of water equivalent to about three times the volume of the mixture may be introduced. In order to mix this without excessive agitation, the water may be pumped into the bottom of the receptacle employed and flow upwardly through the fullers earth carrying with 1t a greater or lesser quantity of oily material. The batch is allowed to stand 5 or 6 hours in order to give opportunity for the oil to collect at the top. The layer is removed in due course by dipping or by means of a skimming pipe.

The proportion of caustic soda (relative to the amount of oily fullers earth), may be varied to meet different conditions of acidity of the oil in the fullers earth. Sufiicient alkali is used to neutralize the free fatty acids, but not toemulsify any considerable proportion of the glycerides. Spent earth from the bleaching of vegetable oils will contain on the average say 20 to 25 per cent of oil. If the earth has not been standing about sov the oil becomes oxidized, a fairly good grade 59 of oil may be recovered in this manner. Too great a proportion of caustic soda causes saponification of the glycerides with the production of an undue amount of soap and the formation of an emulsion which cannot be separated easily. Just enough caustic soda (in the dissolved state) should be used to dislocate the oil from the particles of fullers earth and to neutralize the free fatty acids without forming objectionable emulsions 60 such as would form if much of the oil were saponified by the caustic. 1 or 2 per cent of caustic soda or caustic potash (based on the quantity of the spent fullers earth) therefore usually suffices but the proportions may be increased or decreased according to the nature of the oil, the amount of free fatty acids present, the character of the fullers earth and various other conditions. The salt serves to repress the tendency to form emul- 7o sions (to any great extent), and the proportion of the salt may be varied within considerable limits. A quantity of salt suflicient to salt out the soapat least in large, measure is desirable. On the other hand too 7 large a proportion of salt may render the action of the solution less effective. About 10%, or say from 8 to 15% is usually a satisfactory amount. This percentage isof course based on the amount of the aqueous solution at this stage replaced by other saline substances such as sodium sulphate or other salts or compounds tending to repress emul- I sification of fatty oils in the a ueous liquid.

The-oil obtained may be re ned and any soap produced may be recovered if desired. The requisite proportion of the diluted liquor after removal of the oil may be strengthened by the addition of caustic soda and salt and reused, and in this way some saving is made in the consumption of caustic soda and salt.

Also it is possible to carry out the second step of washing the fullers earth in asomewhat different manner. Instead of the dilution or washing of the fullers earth through the addition of water, an alkaline solution, for example some of the stock solution as set forth above may be pumped through the layer of fullers earth to eliminate remaining oil as far as possible; No considerable proportion of the oil will be saponified or emulsified by this operation. 'After the operation-is completed the aqueous liquor may be again use upon a new quantity of the spent fullers earth, with the addition only of a small amount of caustic soda to bring the NaOH concentration back to about that originally stated.

What I claim is z- 1. The process of separating fatty oil from spent fullers earth which has been used as a bleaching agent for fatty oils, which comprises agitating such spent earth with about an equal amount of a hot aqueous solution containing approximately 2 per cent of caustic soda and 10 per cent of common salt, adding several volumes of hot water to wash out the oil, allowing the mixture to stand until theoil collects at the top and withdrawing the latter.

2. A process of treating spent fullers earth which has been used in refining fatty oils,

vand which contains a considerable amount of fatty oil and impurities removed from such oil, including fatty acids, which process comprises adding to such. earth, an aqueous solution containing a caustic alkali in quantity capable of reacting with the free fatty acids in the saidearth to produce a soap, such solution-being in suflicient amount to dislodge at least a large part of the oil from said earth, such solution also containing a salt which does not chemically react with such soap, and which is of such a character and in such an amount as to be capable of substantially repressing the formation of emulsions of soap solution and oil, the said salt being present in amount substantially greater than said alkali, maintaining such materials hot, long enough to cause reaction of said alkali upon the free fatty acids in said oil to form a soap, and thereafter considerably diluting the material with an aqueous liquid, and finally separating non-saponified oil from the remaining water and substances dissolved therein. I

3. Aprocess of treating spent fullers earth which has been used in refining fatty oils. and which contains a'considerable amount of fatty oil'and impurities removed from such oil,

including fatty acids, which process com-- prises adding to such earth. an aqueous solution containing a caustic alkali in quantity capable of reacting with the free fatty acids in the said earth to produce a soap, and. in

sufficient amount to dislodge at least a large part of the oil from said earth, such solution also containing a saltwhich does not chemically react with such soap, and which is of such a character and in such an amount as to be capable of substantially repressing the formation of emulsions of soap solution and oil, the said salt being present in amount substantially greater than said alkali, maintaining such materials hot, enough to cause reaction of said alkali upon the free fatty acids in said oil to form a soap, and thereafter separating the so purified earth.

4. A process of separating fatty oil from spent earths used in refining fatty oils, which comprises agitating the said spent earths with a dilute hot aqueous solution containing caustic alkali in amount and concentration insuflicient to saponify any large fraction of the glyceride oil present therein, but in amount sufficient to dislodge at least a large part of the glyceride oil from said earth, and a salt which is substantially chemically inert with respect to the oil, caustic alkaliand alkali metal soap formed, such salt being in amount suflicient to substantially repress emulsification of oil in the soap solution formed, diluting the mixture with a hot aqueous diluent which is chemically inert with respect to ,soapand alkali, but which will dissolve soap and alkali, whereby the unsaponified oil is in major part at least dislodged and separated from said earth, and thereby floating the oil out of the said earth.

5. The process of treating spent fullers earth used in refining vegetable oils, which comprises agitating such earth with a hot dilute aqueous solution containing caustic alkali, in amount suflicient to combine with the free fatty acids in the said earth, and sufiicient to dislodge the oil from said earth, but insuflicient to saponify any considerable fraction of the fatty glyceride oil present at the existing temperature, such aqueous solution containing a substantially neutral alkali metal salt in amount capable of repressing emulsification and being heated to near the boiling point, and in pumping through the so-ti'eated mixture a considerable quantity of warm water to wash out the oil from the fullers earth, whereby. oil collects as a layer on the top of said aqueous solution, and may be withdrawn and separated.

6. In the process of treating spent solid absorbent earthswhich have been used in the purification of fatty oil, the improvement which comprises treating such spent sub tendency of the oil to form emulsions in alkaline soapy solutions, the amount of such fixed alkali being insuflicient t0 saponify any large fraction of the fatty oil present. but sufiicient to dislodge the bulk of the oil from the solid absorbent substance, maintaining the liquor hot until the bulk. of the oil has been dislodged from the particles of such spent solid substance, diluting such mixture with aqueous liquid which is substantially without destructive chemical action thereupon, whereby the bulk of the oil is floated 011?, and the soapiness of the liquor is reduced.

I CARLETON ELLIS.