US 3261546 A
Description (OCR text may contain errors)
July 19, 1966 M. E. GRUVER, JR
METHOD FOR CLARIFYING FATS AND OILS Filed Oct. 29, 1962 FIG. 3
FWATER FIG- 2 INVENTOR. MORRIS E GRUVER JR.
ATTORNEY United States Patent 3,261,546 METHOD FOR CLARIFYING FATS AND OILS Morris E. Grover, .lr., Rochester, N. assignor t0 Pfaudler Fermutit Inc, Rochester, N.Y., a corporation of New York Filed Oct. 29, 1962, $er. No. 233,675 2 Claims. (til. 233-20) This invention relates to a method for purifying rendered oils and fats and, more particularly, for removing the solid suspended protein-like material from rendered fats and oils in order to produce a clarified, solid free material.
In the manufacture of fats and oils, the animal waste material comprising fat, scraps of bone and meat, and other protein like waste material is placed in a vessel and subjected to high tempeartures for extended periods of time. This process is known as dry rendering and separates the fats and oils from the protein like material. The product of this process consists of the fats and oils in liquid form combined with a more or less finely divided mass of solid material comprised mainly of .protein Waste material. This protein waste material must be separated from the fats in order to produce a commercially acceptable clear product. The principal object of this invention is the provision of a more practical, economical and controllable process for accomplishing this end.
One of the most common methods of removing the protein waste material for clarifying has been to centrifuge the products as it comes from the rendering kettles. This is an efiicient method of effecting the separation since the protein-like matter differs from the fats and oils in specific gravity and can be removed in the form of a heavy sludge, the fats and oils being taken off as the light, or low density, fraction. However, since the raw material used in this process consists of animal wastes, they are seldom uniform in character or composition, and the amount of protein-like waste material in any given batch of this material can differ markedly; some batches contain very little waste while others may contain a great deal. This has imposed a difficult problem of control of the clarifying or solids removal step since the amount of impurities may differ markedly from batch to batch or throughout the run of any given batch.
The centrifuges used for the clarification step are generally semi-continuous in character; that is, a continuous stream of rendered impure fat is fed to the centrifuge and a continuous stream of clarified fat is takenoft the outlet while the protein like solid materials accumulate in the centrifuge basket in the form of sludge. The sludge eventually builds up to the point where it fills the basket and partially overflows into the clarified fat or effluent conduit and contaminates the same. At this point, the centrifuge feed must be stopped and steps taken to remove the sludge from the basket before the operation can be continued. This step, known in the trade as desludging, is performed by various means depending on the centrifuge design. Most centrifuges have means for automatically performing this step upon actuation of suitable controls.
Heretofore, the difficulty has been in determining the frequency for desludging. Since the product is non-uniform in character, this desludging operation cannot be efficiently performed on a time basis since an arbitrary time cannot be set wherein sufiicient sludge will build up to cause contamination of the product. If desludging is done too frequently, the centrifuge is not utilized to its full capacity; this results in an increase in the cost for this operation. On the other hand, if desludging is not performed sufficiently frequently, contamination of the product results. It is therefore highly desirable to pro- 3,21,546 Patented July 19, 1966 vide a means for reliably determining the proper time for desludging in order to utilize the capacity of the centrifuge to the fullest extent, and to avoid interrupting the process or clarification more frequently than necessary, and at the same time to assure the absence of impurities in the clarified product. The provision of such a means is therefore. a principal object of this invention.
In the past, many attempts have been made to provide automatic control of a fat clarifying centrifuge by means of an instrument which would detect the pressure of minute amounts of sludge or other impurity in the product and then actuate a control for desludging the machine. In particular, since the sludge and the oil differ in density, density measuring instruments have been applied to the output line of such clarifying centrifuge. However, the difference in density between the oil and the impurities is small, and no such instrument was capable of detecting a minute amount of impurity so as to actuate the desludging cycle before a substantial amount of impurity was passed into the product. Similar attempts to measure turbidity and other properties of the effluent clarified oil to detect the first amounts of impurities coming from the centrifuge have been equally unsuccessful because of the great sensitivity needed to detect the first minute amounts of sludge in order to initiate the desludging cycle sufficiently quickly to avoid contamination of the prodnet.
I have found, however, that the sludge or solid products resulting from the clarification of rendered animal fats and oils consists almost wholly of protein matter which has been reduced to a finely divided state by the cooking process in the rendering kettles. Moreover, I have found that this protein has a high afiinity for water, and will absorb many times its own weight of water and carry the same through the process. Moreover, it is a well known fact that water has a radically different dielectric constant from oils and fats and that, therefore, even minute amounts of water (less than .I%) can be detected in streams of oil by means of capacitance meters of known construction. It is, therefore, a further object of this invention to utilize these various properties in order to provide a method for preventing minute amounts of solid material to be carried over into clarified rendered fats and oils in order to initiate the desludging cycle of the clarifying centrifuge as soon as sludge begins to appear in the clarified oil product lines.
Other objects of the invention include provision of method for automatically measuring the quality of the clarified fats and oils and shutting down the feed and desludging the centrifuge Whenever the quality falls below a predetermined value.
Further objects include the provision of means for accomplishing these objects which are simple, inexpensive, positive in operation and completely automatic.
Other objects and advantages of this invention will be particularly set forth in the claims and will be apparent from the following description, when taken in connection with the accompanying drawings, in which:
FIG. 1 is a schematic flow diagram partly in section, showing a centrifugal clarifying apparatus embodying the present invention.
FIG. 2 is a fragmentary view of the centrifuge of FIG. 1 showing the accumulation of oil, water and impurities.
FIG. 3 is a fragmentary view similar to FIG. 2 showing the centrifuge in discharging position.
Referring to the drawings, 10 (FIG. 1) indicates a centrifuge of a type generally used for clarifying fats and oils and removing protein solid matter. This centrifuge forms no part of the present invention and is adequately described in the patent to Nyr-op No. 2,578,- 484 issued December 11, 1951. However, a brief description of this centrifuge will be given at this point in order to clarify the operation of this invention.
The raw products to be purified are fed through a stationary pipe 12 which extends axially into a rotating bowl 14 of centrifuge 10. The feed travels downwardly and outwardly, as shown by the arrows, into the ro rating bowl where the heavier fractions move to the outside under the influence of centrifugal force, while the lighter fractions are displaced inwardly toward the axis of rotation. When the bowl has filled with material, the lighter fractions overflow through annular opening 16 (FIG. 2) whence they pass into the clarified product line 18 (FIG. 1). The heavier fraction or sludge remains near the periphery of bowl 14 until it is removed as hereinafter described.
A series of openings 20 are formed near the portion of largest diameter of the bowl. These openings are sealed by means of an axially moveable ring shaped piston 22 supported in an annular groove 24 adjacent to openings 20. The piston is maintained in position by means of hydraulic pressure in groove 24. When it is desired to desludge the bowl, suitable controls are actuated to relieve the hydraulic pressure in groove 24 holding piston 22 in upward position (as shown in FIG. 1) and the piston moves downwardly uncovering openings 20 (to the position shown in FIG. 3). The contents of the bowl then fly outwardly through openings 20 under the influence of centrifugal force. When the bowl has thus been desludged, the hydraulic pressure is reintroduced to groove 24, moving piston 22 upwardly to a position covering openings 20 and the centrifuge is ready for another cycle. The mechanism constituting this centrifuge and the controls for actuating the desludging operation are described in detail in the above mentioned Nyrop, No. 2,578,484.
As the bowl of the centrifuge fills with the product, the centrifugal force causes a separation into two or more layers. The outer layer S will comprise the heaviest material which is the impurities or sludge comprising finely divided protein like matter. If sufiicient water has been added to the mass, a second water layer W may also build up, but this is not necessarily the case. The inner or lightest layer will comprise the clarified oil. As the bowl begins to fill, the clarified oil begins to pass outwardly through annular opening 16 into oil discharge pipe 18 whence it flows to the finished product storage tanks.
A capacitance product analyzer has been placed in the finished product line. The capacitance product analyzer is a known article, commercially available, and forms no part of this invention. This unit is more fully described by Patents 2,720,624 and 2,717,347 and need not be fully described here. It is sufficient to say that the capacitance of the sensing head 26 of the instrument which is immersed in the product line, is a function of the dielectric constant of the product flowing between spaced insulated electrodes just as the capacitance of any condenser is a function of the dielectric constant of the insulating material between the plates. A tuned electronic oscillator 28 is provided which oscillates freely as long as the capacitance of the sensing head is maintained at a pre-determined value. However, as soon as the composition of the material between the electrodes changes, the capacitance of the sensing head 26 changes, and the resonance of the tuned circuit is destroyed. This actuates an electrical relay 30 which in turn can be used to actuate the centrifuge controls to shut off of the product line and desludge the centrifuge.
As bowl 14 fills with sludge (or sludge and water).
the oil interface moves progressively inwardly, towards the axis of rotation, to the position shown in FIG. 2. At this time, small amounts of Water (or water saturated sludge) begin to pass out through opening 16 into line 18.
It is Well known that the dielectric constant of oil and water are considerably different. Water, particularly in the impure state, is a fair conductor of electricity; dry oil is a good insulator with a very high dielectric constant. Thus, it has been found that the inclusion of as little as .1% moisture in a stream of oil can readily be detected by the change of the capacitance controller such as that described in the above mentioned patents.
An important point of this invention is the addition of water to the strongly hydrophylic protein-like base material prior to centrifuging. The protein immediately absorbs the Water, swelling to several times its original volume. Thus, the inclusion of even a small amount of the protein like impurity with its absorbed water in the product line will be suflicient to actuate the capacitance relay to initiate the desludging cycle.
Upon initiation of the desludging cycle, relay control 30 shuts off the flow of impure rendered oil to the centrifuge and initiates the downward movement of the cylindrical piston 22. This uncovers openings 20 of the centrifuge and causes the sludge contained in bowl 14 to fly out as shown in FIG. 3. As soon as the centrifuge has been completely desludged, control 30 causes cylindrical piston 22 to move axially to cover ports 20, and at the same time, open the valve to initiate the flow of raw impure oil to the centrifuge and the cycle is repeated.
Thus, it can be seen that this invention attains its stated objects. The cycle is completely automatic and acts to desludge the centrifuge as soon as even a minute amount of impurity appears in the clarified oil product line. The sensitivity of the capacitance controller in de tecting water saturated protein impurities is such that no significant amount of impurity can pass through the controller to the finished product line before the desludging cycle is initated. At the same time, the operation of the centrifuge by a desludging cycle is avoided until the centrifuge has removed all the impurities it can contain and thus, the centrifuge is utilized to the highest possible eflficiency. The apparatus is simple, economical and reliable and operates fully independently of any human control.
While I have shown and described the preferred form of mechanism of my invention it will be apparent that various modifications and changes may be made therein, particularly in the form and relation of parts, without departing from the spirit of my invention as set forth in the appended claims.
1. A method for clarifying dry rendered fat containing hydrophylic impurities comprising the method steps of adding water to the said impure fat, centrifuging impure said fat-water mixture for separating said dry rendered fat from water and impurities, continuously drawing off said separated fat from said centrifuge, measuring the dielectric constant of said separated fat to detect the presence of water, and removing the accumulated impurities and water from said centrifuge when water is detected in said separated fat.
2. A method for separating immiscible high and low density components of their mixture comprising the method steps of adding an additional component to said mixture, said additional component having a dielectric constant differing from said low density component and a density intermediate said high and low density components, and said additional component being immiscible in said low density component, centrifuging said mixture and said additional component to separate said low density component from said high density component and said additional component, continuously drawing off said low density component from said centrifuge, measuring the dielectric constant of the low density component material drawn off to detect the presence of said additional component therein, and removing the accumulated high density component and additional component 5 6 from said centrifuge when said additional component is 2,823,215 2/ 1958 Downing 260412.6 detected in said material drawn off. 2,933,657 4/ 1960 Maltby et a1 324-61 3,013,572 12/1961 Lahti et a1. 137-93 References Cited by the Examiner 3,020,160 2/ 1962 Downing et a1. 260--412.6 X Steinbacker 2,216,680 10/1940 Thurman 260428 FOREIGN PATENTS 2,467,742 4/1949 HEIIIIIO 233-20 105 479 9 1942 Sweden 2,532,792 12/1950 Svensjo 23319 2,576,253 11/1951 Farrell et al. 13793 10 M. CARY NELSON, Primary Examiner. 2,578,484 12/1959 Nyrop 23320 2,618,644 11/1952 Bailey 260 428 CHARLES PARKER Exammer' 2 628 023 2 1953 Dahlstedt 33 19 A. SUTTO, H. KLINKSIEK, Assistant Examiners.