US3706571A - Blood separation process - Google Patents

Abstract

A CONTINUOUS PROCESS FOR COAGULATING AND SEPARATING BLOOD SOLIDS FROM A LIQUID. THE LIQUID IS PASSED UNDER PRESSURE THROUGH A VESSEL IN WHICH THE LIQUID IS HEATED BY STEAM INJECTION TO A TEMPERATURE ABOVE ABOUT 190*F. BUT BELOW ITS BOILING POINT. THE HEATED LIQUID IS RETAINED UNDER PRESSURE IN THE VESSEL FOR AT LEAST FIVE SECONDS AND THEN IS DISCHARGED THROUGH A PRESSURE REDUCER TO A SEPARATOR WHEREIN THE COAGULATED BLOOD SOLIDS ARE EXTRACTED FROM THE LIQUID.

Description

DeC. 19, E 1 DUFAULT BLOOD SEPARATION PROCESS Filed July 20, 1970 LIQUID EFFLUENT WET BLOOD SOLI DS FIG. 1

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INVENTOR.

EMMANUEL J. DUFAULT ATTORNEY United States Patent O 3,706,571 BLOOD SEPARATION PROCESS Emmanuel J. Dufault, Pittsford, N.Y., assigner to Sybron Corporation, Rochester, N.Y. Filed July 20, 1970, Ser. No. 56,428 Int. Cl. A231' 1/06; A23k 1/04 U.S. Cl. 99--21 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to a process for treating liquids containing blood solids and more particularly to a continuous process for coagulating the blood solids by steam injection and extracting the coagulated solids from the liquid.

Blood is a byproduct of the packinghouse; meat, poultry, and fish processing; and rendering industries. The blood that is recovered in these operations is usually diluted with Water and contains various impurities. It has a relatively low value, but with processing it can be used in the preparation of animal feed, glue or fertilizer. The major use of this grade of blood is in the preparation of dry animal food, in which dried blood solids are used as a protein supplement.

In the past the standard method of recovering the blood solids from this grade of blood has been to heat the blood in a large vessel to drive olf the moisture while agitating the blood to keep the solids from coagulating into a solid mass. This method suffered from several disadvantages. The blood solids were recovered in the form of a dry, line powder that was very difficult to handle. lThe process required a long time and was rather inefficient. Finally, the long heating period reduced the nutritional value of the dried blood.

Recently, attempts have been made to avoid these problems by continuous processes for coagulating and separating the blood solids. In typical processes, the blood passes through a vessel where it is heated to coagulate the solids and into a scroll type centrifugal decanter, filter, press or similar separator where wet blood solids are recovered. The blood is usually heated by direct steam injection because of the rapid heating provided by and the low cost of steam heat.

These steam injection processes are faster and more economical than the old heated vessel processes, but they have not been adopted very widely because they have not produced uniform results under varying conditions. Systems of this type are usually called upon to handle many different types or fractions of blood and because of the conditions under which blood is collected in packinghouses and similar establishments, these systems frequently must handle blood that has been diluted with substantial amounts of water and/or contains various impurities. Prior continuous steam injection processes have been extremely sensitive to the amount of dilution, the type of blood being treated and various other factors. Sometimes the processes worked satisfactorily, but under dilferent conditions the coagulated solids would be so small that ice they could not be separated readily. Even with the addition of coagulation promoting chemicals to the blood, consistent results have not been achieved under all conditions.

OBJECTS OF THE INVENTION It is an object of this invention to provide a more effective continuous process for separating blood solids from a liquid.

It is another object of this invention to provide a continuous, steam injection process for coagulating, without adding chemicals, the blood solids in a wide variety of liquids.

Another object of this invention is to provide a process for recovering blood solids in a form in which they can be easily handled by a wide variety of equipment.

A still further object of this invention is to provide a process for separating blood solids from a liquid with minimal reduction of the nutritional value of the solids.

SUMMARY OF THE INVENTION I have discovered that continuous steam injection processes will effectively coagulate the blood solids in a wide variety of liquids; including whole blood, mixtures of whole blood from different animals, whole blood that has been diluted with Water, and liquid blood fractions such as the serum and hemoglobin fractions produced by centrifuging whole blood; if the liquid is kept from boiling for a brief period of time after the steam is injected. This apparently keeps the solids and liquids from separating until the solids have coagulated enough to form relatively large particles.

This may be accomplished by passing the liquid under pressure through a pressure vessel wherein the liquid is heated by steam injection to a temperature above about F. but below its boiling point. Temperatures in the 220-260 F. range are preferred because the blood solids coagulate more rapidly and more uniformly at these higher temperatures. One of the advantages obtained by holding the liquid under pressure during the heating step is the ability to utilize higher temperatures.

The size of the pressure vessel and the ow rate through the vessel must be adjusted to retain the liquid in the vessel for a sufficient period of time after it has been heated to produce the desired amount of coagulation. The minimum retention time will be inversely-proportional to the temperature. Under most conditions, the liquid should be kept in the vessel for a period of at least five seconds. Retention times of 10-20 seconds are preferred.

In order to keep the liquid from boiling in the vessel, the liquid must be introduced into the vessel under a pressure above its vapor pressure at the temperature to which it will be heated. Typically, pressures of 15-45 p.s.i.g. are employed in order to provide a satisfactory operating margin.

The desired pressure is maintained in the vessel by discharging the liquid through a pressure reducer such as a manual or automatic back pressure valve or an orifice plate. Automatic back pressure valves are preferred because they will hold a fairly constant pressure in the vessel under varying ow conditions, however, if the operating conditions are steady, simpler and less expensive pressure reducers may be used.

The discharged liquid goes through a separator such as a scroll type centrifugal decanter, filter or the like wherein the coagulated blood solids are extracted from the liquid. The coagulated solids are recovered in the form of relatively large wet akes which, because of their size, can be further processed by a wide variety of driers and material handling systems.

3 DETAILED DESCRIPTION FIG. 1 is a schematic diagram of one form of apparatus for practicing the process of this invention.

FIG. 2 is a diagrammatic sectional elevation of the separator used in the apparatus of FIG. 1.

Referring to FIG. 1, a liquid containing blood solids is forced by pump 1 through pipe 2. Steam is injected through standard 45 pipe fittings 3 into the pipe to heat the liquid to the desired temperature. A temperature of 220-260 F. is usually maintained in the pipe downstream from the steam injectors.

The desired pressure is maintained in the pipe downstream from the steam injectors by an automatic, air operated back pressure valve 4. Typically, the pressure in this section is 15-45 p.s.i.g.

The back pressure valve is placed far enough downstream from the steam injectors to maintain the liquid at the elevated temperature and pressure for the desired period. Typically, this period is l20 seconds, but shorter or longer periods may be employed.

The liquid tlows through the back pressure valve 4 to a scroll type centrifugal decanter S. As shown in FIG. 2, the decanter has a conical bowl 6 and a scroll 7 coaxial with and inside the bowl 6. A helical screw 8 around the periphery of scroll 7 just clears the inside of bowl 6. 'I'he scroll 7 and bowl 6 are rotated in the same direction by a motor (not shown). The scroll rotates at a slightly higher speed than the bowl.

The liquid enters the decanter through a hollow center shaft 9 and is accelerated by the spinning scroll 7 and bowl 6 to the rotating speed of the bowl. Centrifugal action forces the heavier coagulated solids 10 against the sides of the bowl, while the remaining liquid forms a supernatant layer 11 above them.

'Ihe blood solids 10 are conveyed by the helical screw 8 on scroll 7 to the small end of the conical bowl 6 and ejected through a discharge chute 12. The solids leaving the chute 12 are in the form of small wet tlakes which are much easier to handle than the powders produced by prior art processes. 'Ihese akes are dried in a rotary drum drier (not shown) and collected in a cyclone (not shown). The solids discharged form the cyclone are still in the flake form.

While the wet blood solids 10 are being carried out of the decanter by scroll 7, the remaining liquid 11 collects in the larger end of bowl 6, where it overflows a regulating ring 13, and enters a pumping chamber 14 where its kinetic energy is converted to pressure which forces it out of the decanter through line 15.

Of course, many modifications may be made to this system. 'I'he foregoing description and the following examples are merely illustrative and are not intended to limit the scope of this invention.

EXAMPLE I Diluted whole beef blood -was pumped through a one inch pipe at a rate of 1.75 gallons per minute and a pressure of 30-35 p.s.i.g. The temperature in the pipe was maintained at 230-235 F. by steam injection. The blood was discharged through a back pressure valve, located eight feet downstream from the last steam injector, into a scroll type centrifugal decanter with an inside bowl diameter of nine inches and a bowl length of 17 inches. The bowl speed was 5400 r.p.m. and the scroll speed was 5448 r.p.m. 37.8% of the diluted whole blood was collected as wet blood solids containing 40% moisture by weight. The liquid discharged from the decanter contained an average of 2.5% solids.

EXAMPLE II Another test was conducted using beef blood which had been diluted by adding 30% by weight of water and operating the system described in Example I at a ow rate of 2 g.p.m., a temperature of 220 Fi, a pressure of 22-35 p.s.i.g., a decanter bowl speed of 3000 r.p.m. and a decanter scroll speed of 3020 r.p.m. 37.1% of the original diluted blood was collected as blood solids containing 64.2% moisture. The liquid effluent from the decanter contained an average of 3.8% solids.

EXAMPLE III A third test with beef blood, again 30% diluted by the addition of Water, was run on the same system at a ow rate of 2 g.p.m., a temperature of 230-240 F., a pressure of 20-30 p.s.i.g., a decanter bowl speed of 3000 r.p.m. and a decanter scroll speed of 3020 r.p.m. The liquid effluent from the decanter contained an average of 2.6% solids. 33.4% of the original diluted blood was collected as blood solids containing 56.2% moisture.

EXAMPLE IV A diluted mixture of beef, hog and lamb blood was pumped at a rate of 9000 lbs. per hour and a pressure of 20 p.s.i.g. through a 2 inch pipe. Steam was injected into the line to heat the mixture to a temperature of 245 F. The -back pressure valve was located 24 feet from the last steam injector.

The coagulated blood solids were extracted by scroll type centrifugal decanters operating at a -bowl speed of 2100 r.p.m. and a scroll speed of 2115 r.p.m. The liquid effluent from the decanters contained an average of 1.2% solids.

EXAMPLE V The system used in Example IV was operated at the same temperature, pressure, bowl speed and scroll speed but with a diluted blood flow rate of 6000 lbs. per hour. The liquid elliuent from the decanters contained an average of 0.9% solids.

I claim:

1. A continuous process for separating blood solids from a liquid comprising:

(a) passing the liquid under pressure into a pressure vessel, said pressure bein-g above the vapor pressure at the temperature to which the liquid is heated;

(b) heating the liquid by steam injection to a temperature above about F. but below its boiling point while maintaining the liquid under pressure;

(c) retaining the heated liquid under pressure in the vessel for a period of at least ve seconds, whereby the -blood solids are coagulated under pressure; and

(d) discharging the liquid through a pressure reducer to a separator wherein the coagulated blood solids are extracted from the liquid.

2. A process according to claim 1 wherein the liquid in the vessel is at a pressure of 15-45 p.s.i.g.

3. A process according to claim 1 wherein the liquid is heated to a temperature of 22o-260 F.

4. A process according to claim 1 wherein the heated liquid is retained in the vessel for 10-20 seconds.

5. A continuous process for separating blood solids from a liquid comprising:

(a) pumping the liquid through a pipe under a pressure above the vapor pressure at the temperature to which the liquid is heated, and heating the liquid by steam injection to a temperature above about 190 F. but below its boiling point while maintaining the liquid -under pressure;

(b) retaining the heated liquid under pressure in the pipe for a period of at least about five seconds, whereby the blood solids are coagulated under pressure; and

(c)discharging the liquid through a back pressure valve to a scroll type centrifugal decanter wherein the coagulated blood solids are extracted from the liquid.

6. A process according to claim 5 wherein the liquid is pumped through the pipe at a pressure of 15-45 p.s.i.g.

7. A process according to claim 5 wherein the liquid is heated to a temperature of 22g-269 F.-

8. A process according to claim 5 wherein the heated liquid is retained under pressure in the pipe for 10-20 seconds.

9. A continuous process for coagulating and extracting blood solids from a liquid comprising:

(a) pumping the liquid at a pressure of 15-45 p.s..g. through a pipe, said pressure being above the vapor pressure at the temperature to which the liquid is heated, and heating the liquid to a temperature in the range of 220-260" F. but below its boiling point while maintaining the liquid under pressure;

(b) retaining the heated liquid under pressure in the pipe for a period of 10-20 seconds, whereby the solids are coagulated under pressure; and

(c) discharging the liquid through an automatic back pressure valve to a scroll type centrifugal decanter wherein the coagulated solids are extracted from the liquid.

References Cited UNITED STATES PATENTS 3,450,537 6/1969 Filstrup 99-21 2,165,721 7/1939 Norman 99-21 10 3,123,593 3/1964 Allan et al. 99-21 X 3,431,118 3/1969 Macy et al. 99-21 X RAYMOND N. JONES, Primary Examiner

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