Fat and protein removal from process streams

Details Fat and protein removal from process streams Fat and protein removal from process streams

2000-06-05

2002-04-16

Hruskoci, Peter A. (Department: 1724)

Liquid purification or separation

Processes

Making an insoluble substance or accreting suspended...

C210S725000, C210S727000, C210S730000, C210S734000, C210S905000, C426S657000, C530S420000, C530S421000, C530S859000

Reexamination Certificate

active

06372145

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to methods or process for the precipitation and removal of fat and protein which contribute to the chemical oxygen demand (“COD”) or biological oxygen demand (“BOD”) from a wide range of process streams along with the removal of other suspended solids. This process utilizes the unique characteristics of the aluminate ion (Al(OH)
4
−
) to facilitate efficient, cost effective removal of the quite valuable fat and protein.
The presence of fat and protein in industrial process streams represents significant environmental problems due to the COD/BOD levels resulting from the fat and protein's presence since these materials are aerobically decomposed. These components decompose slowly but still contribute significantly to the COD burden of a given stream. Additionally, the presence of fats in process streams coats the process equipment and prevents this equipment from functioning at peak efficiency.
Increasingly stringent regulations on the COD/BOD levels in water which can be discharged into the environment places many facilities presently outside of compliance with these environmental regulations. The presence of fat and protein components in any given process stream may result from a wide variety of input sources and is commonly found in waste water from animal slaughterhouses and food processing facilities.
Equally important to the environmental problems these fat and protein components can create, they inherently have value within the marketplace. Therefore, recovery of the large amounts of these materials which is presently being lost would potentially create additional sources of revenue to a large number of facilities.
The relatively large pieces of pure fat may be, and typically are readily removed through filtration, floatation or settling. However the small, suspended and dissolved fat and protein components intermixed with other suspended solids such as dirt, silica, each other or any other process component typically cannot be removed by simple filtration, flocculation, or settling. Consequently more extreme measures must be taken in order to remove these suspended particles.
It is known that acid hydrolyzing metal salts such as iron, particularly when added as ferric (Fe
3+
), can be used as a flocculation agent, but the iron then acts as a catalyst for the auto-oxidation of the fatty substances and thereby reduces the value of the subsequently recovered materials. The art also teaches that aluminum, particularly when added as free, uncomplexed aluminum ion (Al
3+
), like the iron, also acts as a catalyst for the auto oxidation of the fatty substances. This auto-oxidation of the fatty substances is particularly problematic where the recovered materials are rendered. During rendering the recovered fatty materials are cooked to remove the water and melt the fat, thereby creating a rough separation of the fat from the other materials. Ultimately the recovered materials can be used as animal feed, and if the recovered fat is of sufficient quality it can also be sold as tallow, with its purity determining its market value.
Some facilities presently resort to simply dumping large quantities of high COD creating fat and protein containing water into municipal water systems, thereby placing significant strain on downstream purification processes. Other facilities must construct large dumping ponds into which the waste water is pumped. While such ponds prevents the waste water from introduction into lakes, rivers and streams, it not only prevents the reuse of large volumes of process water and can result in the release of significant odors which make it undesirable in even sparsely populated regions, but these ponds ultimately fill with organic sediment and require routine and costly dredging.
Other processes, such as ultrafiltration, can ultimately remove almost any suspended solid particle, even the suspended fat and proteins. While ultrafiltration can reduce the total suspended solids (TSS) within a process stream, it is typically unable to effectively reduce the COD content created by dissolved particles and components, sometimes referred to as the total dissolved solids (TDS).
While traditional and known methods can significantly reduce the quantity of water required in a given process and prevent the discharge of high COD water into the environment, the high cost of capital equipment, maintenance and operation make such processes prohibitively expensive for a large number of applications.
A process capable of easy, efficient removal of suspended fat and protein components from a wide range of industrial process streams thereby allowing not only the discharge of said streams into the environment or reuse and recycle of said streams, but also facilitating recovery of the discarded fat and protein materials would be a great advancement in the art.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention provides a method or process for the precipitation or coagulation and easy removal of suspended fat and protein containing particles and components, which organic matter creates high quantities of Chemical Oxygen Demand (“COD”) or Biological Oxygen Demand (“BOD”), as well as other suspended solids from a given solution. The process includes the addition of aluminate, typically added as sodium aluminate Na(Al(OH)
4
)), followed by the addition of a flocculating agent, typically anionic or cationic polymers such as polyacrylamides, polycarboxylates, and polyamines or even the naturally occurring polymer pectin.
Once the aluminate is added a flocculating agent is then added to create large, suspended flocculate particles. The precise solution pH will be a function mainly of the quantity of aluminate added and the type of flocculating agent used. Generally, after the aluminate is added the solution pH will be between about 4 and 10. Where cationic flocculating agents are used, the pH of the solution will generally be between about pH 4 and 8 when the flocculate is formed, although, since the cationic flocculating agents are not as pH sensitive as their anionic counterparts, the cationic flocculating agents are capable of effective removal up to about pH 9-10. Where anionic flocculating agents are used, the pH of the solution will generally be greater than about pH 5 when the flocculate is formed.
One skilled in the art will recognize that because aluminate itself (as well as other bases) can be used to raise a solution's pH, even solutions whose pH is considerably below 4 can be effectively treated. Additionally, while removal of the protein and fat components is not as complete where the aluminate is added above pH 8, removal can nonetheless be effected even at pH's above 10.
The flocculating agent's interaction with the aluminate associated with the fat and protein components produces a large, neutral and substantially organic complex which is insoluble in the solution and which will more easily precipitate or coagulate so as to assist in removing the fat and protein materials from the solution. As the flocculating agent precipitates the fat and protein components, it will also capture the other suspended solids such as silica, dirt, etc.
Different types of flocculating agents can be employed to produce the desired precipitation. Typically, large synthetic organic polymers will be used depending on the quantity of aluminate used, and the solution pH. Additionally, naturally occurring polymers, such as pectin, can also be used as a flocculent to provide an all “natural” process free of “man-made” chemicals.
Once the suspended fat and protein components have been precipitated into larger, more easily filtered particles, they can be readily removed by flotation, filtration or other known methods in the art.
Once the fat and protein have been removed from the process stream, this material can be either immediately used as animal feed, or it can be rendered. The process of rendering heats the recovered material, driving out the noncomplexed water and can be further used to melt

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