The present invention relates generally to a process of recovering useful materials from waste sources that include Dried Distillers Grains with Solubles also known by the acronym DDGS, waste materials from ethanol production and animal feed waste.
Thin stillage and distillers' grains are byproducts remaining after alcohol distillation from a fermented cereal grain mash. Both byproducts are used as energy and protein sources for ruminants. There are two main sources of these byproducts. The traditional sources were from brewers. However, more recently, ethanol plants such as corn, sugar cane, cassava and potatoes have become a growing source.
DDGS contain valuable bio-materials mainly fibers, oil and protein. The oil in DDGS could be used either as cooking oil or as a biofuel. The main protein in corn is Zein which has been used in the manufacture of a wide variety of commercial products, including coatings for paper cups, soda bottle cap linings, clothing fabric, buttons, adhesives, coatings and binders, recently this protein has been used as a coating for candy, nuts, fruit, pills, and other encapsulated foods and drugs. Additionally Zein can be further processed into resins and other bioplastic polymers. Fibers may be used as raw materials in the production of lignocellulosic ethanol. Residue materials from ethanol production contain fibers from which ethanol has been extracted. However, only about 50-70% of the ethanol in these materials is typically extracted leaving substantial portion of ethanol that is available for further extraction. Tables 1 and 2 provide a typical content breakdown of the various materials in DDGS.
It would therefore be desirable to provide a process to separate these materials in order to maximize their uses.
In an aspect of the present invention, a multi-stage substantially continuous process for separating a source stream intermixedly containing fibers, proteins and oil, the process being configured for separating the source stream into three streams each containing predominantly one component, the source stream containing Dried Distillers Grains with Solubles, the process comprises the stages of: providing a first stream comprising dried distillers grain with solubles, the dried distillers grain stream containing water, oil, protein and fibers, the fibers containing hemicellulose and cellulose components; separating a stream comprising predominantly proteins and a mix of oil in a water that form an stream comprising predominantly fiber materials from the source stream; separating a stream containing predominantly oil and a stream containing predominantly proteins from the water with oil; and progressively concentrating the stream containing predominantly proteins in at least one additional step.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.
The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention.
Raw Dried Distillers Grains with Solubles (DDGS) typically contain water in the range of between about 85% to about 95%, but could also be higher or lower depending on the source. Targeted polymers are added to the process to accomplish two objectives:
a. Detach the oil molecules from the fibers. The oil is held in the open pores of the fibers and also tends to have a strong affinity to the fiber surfaces.
b. Separate water and solids from a generally a mixture of oils fats and protein. Depending on the composition of the mixture, this may require several steps wherein the protein is progressively removed from the mixture.
c. Separate four streams from the source stream containing DDGS: 1) a stream containing predominantly oil, 2) a stream containing predominantly cellulose and hemicellulose fibers, 3) a stream containing predominantly protein and 4) an effluent stream of predominantly water that may be discarded and, as such, must comply with COD and BOD regulations. In this context, a predominant content of a component means at least 75% by weight of the component in the stream.
The targeted polymers selected to aid in stream separation possess colloidal properties that make them conducive for components of the stream to agglomerate around these polymers. The process of the present invention comprises of two distinctly different embodiments depending on the pH of the DDGS which is largely a function of the source and the treatment the DDGS undergoes prior undergoing the process of the present invention. For DDGS having a pH higher than about 5, the chemical additives required for effective separation are different than those required for DDGS having a pH below about 5. These are described below in more detail, but the underlying processes and the end results they intend to accomplish are the same.
A. Separating Fibers From a Water Mixture of Protein and Oil From the DDGS Source Stream
In this stage, the DDGS source stream is treated sequentially with two polymers or a silicate depending on the pH and passed through a rotary screen. This produces 1) a relatively high solids stream rich in fibers stream that may contain small amounts of proteins and oil and 2) and a stream containing low non-aqueous fluids that is a mixture containing protein and oil. The low solids stream may contain from about 0.5 percent to about 5% solids. The high solids stream may contain about 25% to about 35% solids with the liquid portion comprising predominantly of water and smaller amounts (typically less than 15%) of protein. This fraction is expected to be substantially oil free.
The high solids stream may undergo a second protein recovery step. A multi disk press further removes a mixture of protein and concentrates the high solids fiber fraction to a range between about 40% to about 50% solids.
The fibers may undergo further treatments as will be described below.
B. Recovery of the Oil and the Protein From the Water a Mixture Containing the Protein and the Oil
In this phase, the oil is recovered in a clarifier aided by a polymeric addition to the mixture and optionally an oil skimmer that removes the oil that rises to the top of the clarifier. The protein and water is passed through a Dissolved Air Floatation Device (DAF) with micronized air where further separation of oil and protein takes place. A multi disk press concentrates the protein fraction from the DAF and removes water effluent that is substantially oil free.
The protein fraction streams originating from the multi stage removal steps may be combined into one stream.
C. Fiber Treatments
The fibers are treated in a pin macerator to prep them for further biofuel production as will be described below.
The polymers used in the process of the current invention selectively steer the protein and oil components to the low solids streams containing mostly water.
The following represents the important characteristics of these polymers used in the process.
Polydicyandiamide is obtained from the reaction of Dicyandiamide monomer and formaldehyde as shown below:
This polymer may be made from the reaction between an acrylamide monomer and an acrylic acid monomer as shown below.
The anionicity of these copolymers can vary between 0% and 100% depending on the ratio of the monomers involved. The anionic copolymers used in the process of the present invention may have a molecular weight ranging between about 3 million to about 30 million, and a viscosity at a concentration of 5 g/l ranging from about 200 centipoises to about 2800 centipoises. The preferred pH range for making these copolymers is from 4.5 to 9. It is also noted that potassium may be substituted for the sodium as the base in the Acrylate Acrylamide copolymer.
The process of the present invention is described in
In the embodiment displayed in
In another embodiment of the present invention, the process may optionally further comprise adding between about 5 ppm to about 25 ppm of a silicate to a silicate addition inlet placed in the first chemical additive pipe. The silicate inlet precedes the first inlet in the first chemical additive pipe. The silicate may be sodium silicate, calcium silicate, magnesium silicate, potassium silicate or silicon dioxide.
The third stream undergoes a further split in a multi-disk press that generates a 10th stream that has a percent solids content of between about 45% to about 55% solids and contains mostly cellulose and hemicellulose fibers and a 9th stream containing mostly water with small amounts of protein that might still be present that may range from about 2% to about 10%.
The second stream is moved toward a clarifier through the 2nd pipe that has the 3rd and 4th chemical addition inlets. The 4th inlet is placed about 15 seconds after the 3rd inlet calculated based on the average volumetric flow rate through the 2nd pipe. About 5 to about 25 ppm of cationic polyamine, 50% charge and 1 million MW is fed into the 3rd inlet and 5-25 ppm anionic acrylamide copolymer 14-22 million MW are fed into the 4th inlet. The clarifier splits the 4th stream into the 6th stream containing predominantly protein and water and the 7th stream that contains predominantly oil. A skimmer may be used to collect the oil from the top of the clarifier as will be described below. The sixth stream is fed into a Dissolved Air Floatation Device (DAF) through the third pipe that contains the 5th and 6th chemical addition inlets prior to the DAF. The 6th inlet is placed about 15 seconds after the 5th inlet calculated based on the average volumetric flow rate through the 3rd pipe. About 5 to 25 ppm of polydicyandiamide having about 100,000 weight average MW and having a cationic charge are added to the 5th inlet and about 5-25 ppm anionic acrylamide copolymer having a weight average MW of 18-25 million are added at the 6th inlet. All ppm are calculated on a weight basis.
The DAF separates the 6th stream into an 8th stream rich in protein with >70% of the stream composition and a water and residue stream shown as the le stream containing predominantly water and less than 15% protein. Streams 9 and 14 may be combined as they have similar compositions. The combination of these two streams forms stream number 11. The 11th stream is treated in a multi disk press with about 5-25 ppm acrylamide-dimethylaminoethyl acrylate copolymer (ADMAEA) added to the 7th inlet at the multidisc press or in a pipe prior to the multi-disk press. This stage further separates a 13th stream containing over 80% protein from the 11th stream that also generates an effluent stream comprising of mostly water. Any residual oil present in the 6th stream may be collected as it rises to the top of the DAF using an oil skimmer.
In this embodiment of the present invention, two steps of protein separation are performed, wherein protein is progressively removed from the liquid portion of DDGS using suitable polymers in each stage configured for coalescing protein molecules and remove from a source stream. The 8th and 13th streams are rich in protein in excess of 75% by weight and may be combined into one stream, then taken for further processing as needed in order to utilize the materials.
The 10th stream containing cellulose and hemicellulose fibers at solids exceeding 45% by weight may further be treated in a pin macerator according to the process disclosed in U.S. Pat. No. 8,444,810. This treatment macerates the fibers in a way that allows further extraction of ethanol-biofuels and other chemicals in subsequent steps. Typical addition levels for the polymers used in this process is between 5 ppm to about 25 ppm and preferable between about 10 ppm to about 20 ppm, the DAF must be equipped with micronized air as essential part of the DAF system. Suitable equipment used in this process, i.e., the centrifuge, clarifier and DAF may be of any type currently used in the art.
In both the clarifier and the DAF device, the oil tends to rise to the top of the solids fraction as it is lighter than the protein fraction. An oil skimmer may optionally be used to skim off the oil; oil skimmers are currently known in the art and a number of suitable skimming devices may be used for this purpose. Skimming aids may be optionally added to help with agglomerating the oil to facilitate it being skimmed off. Sulfonic acids such as Nonylphenol, (ethoxylated) ethanol acid with the chemical formula of or sodium dodecylbenzenesulfonate having the formula C15H24O.(C2H4O)n are surfactants that are suitable for this purpose. Likewise, silicon dioxide, SiO2, is suitable as an oil skimming aid. These aids may be added with the polymers.
The embodiment presented in
The clarifier separates the 4th stream into a 6th stream rich in protein with >70% of the stream composition, and a 7th stream rich in oil with >70% content of the composition. The 4th stream may contain between about 10% to about 20% protein while the fifth stream contains over 90% water.
With both embodiments illustrated in
In the process described in
It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention.
This application is a continuation in part application claiming priority from non-provisional application Ser. No. 13/929,618 filed on Jun. 27, 2013.
Number | Date | Country | |
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Parent | 13929618 | Jun 2013 | US |
Child | 14190332 | US |