Process and method for stillage fermentation

Abstract

The present invention generally relates to a novel process in which thin stillage is processed to produce algae oil and protein rich biomass as well as other energy rich byproducts. In accordance with a preferred embodiment, thin stillage is removed from an evaporator during the evaporation process to produce mid-stillage. This mid-stillage is preferably routed to a new process where it is directed to a pre-treatment centrifuge to remove suspended solids, sludge and corn oil. Thereafter, the mid-stillage is preferably cooled and then directed to a fermentation tank where the mid-stillage is subject to a batch fermentation process with algae “seed” fed from an algae inoculation system. Once the batch is harvested, the oil-rich algae/mid-stillage is then preferably heated to rupture the cells and liberate the oil. Thereafter, the oil-rich algae/mid-stillage is preferably processed by a centrifuge which produces solids, a light phase oil and a “clean” mid-stillage stream that can be evaporated to a very high level of solids.

1 . A process of producing bioproducts following the distillation of biomass, wherein the process comprises the steps of:
 separating ethanol and whole stillage;   routing the whole stillage to a centrifuge;   centrifuging the whole stillage to remove solids and to produce a thin stillage, wherein the thin stillage is comprised of 5-8% solids;   routing the thin stillage to an evaporator;   evaporating water content from the thin stillage to produce mid-stillage, wherein the mid-stillage is comprised of 9-27% solids;   separating the mid-stillage into light phase oil, a sludge layer and clarified mid-stillage, wherein the clarified mid-stillage is in water phase with less than 1% suspended solids;   cooling the clarified mid-stillage;   routing the clarified mid- stillage to an algae fermentation tank;   adding algae seed from an algae inoculation system to achieve a starting concentration of 1.5-3.0 grams/L algae;   injecting air into the algae fermentation tank to support an aerobic chemical process;   maintaining a temperature in the range of 25-35° C.; and   harvesting oil-rich algae from the algae fermentation tank after a fermentation period.   
     
     
         2 .- 13 . (canceled) 
     
     
         14 . The process of  claim 1 , wherein the mid-stillage is comprised of 13-17% solids. 
     
     
         15 . The process of  claim 14 , wherein the light phase oil is further processed to produce ethanol. 
     
     
         16 . The process of  claim 15 , wherein the sludge layer is removed and directed to an oil recovery system to produce additional oil. 
     
     
         17 . The process of  claim 16 , wherein the step of cooling the clarified mid-stillage cools the clarified mid-stillage from an incoming temperature of 60-85° C. to a temperature in the range of 25-35° C. 
     
     
         18 . The process of  claim 17 , wherein the step of cooling the clarified mid-stillage is performed using an energy recovery algae process feed heat exchanger with a cooling stream supplied from the algae fermentation tank. 
     
     
         19 . The process of  claim 18 , wherein the clarified mid-stillage is cooled further in a second cooling step wherein the cooling is applied in the form of a cooling water heat exchanger. 
     
     
         20 . The process of  claim 19 , wherein the seed algae is comprised of one or more algae selected from the group of algae comprising: algae of the  Chlorella  genus,  C. protothecoides, C. vulgaris, C. sorokiniana, C. saccharofila, Chlamydomonas reinhardtii, Chlorococcum littorale, Platymonas subcordiformis, Anabaena, Nostoc muscorum, N. spongiaeforme, Westiellopsis prolifica, Oscillotoria  Miami BG7 and  Aphanothece halophytico.    
     
     
         21 . The process of  claim 20 , wherein the harvesting process comprises the steps of:
 heating the oil-rich algae to approximately 85-99° C.;   wherein the step of heating the oil-rich algae comprises a first step of adding heat recovered from incoming mid-stillage.   
     
     
         22 . The process of  claim 21 , wherein algae oil from the oil-rich algae is recovered by a 3-phase centrifuge which produces light phase oil, clean mid-stillage and at least one of sludge or solids. 
     
     
         23 . The process of  claim 22 , wherein the light phase oil is separated as vegetable oil or biodiesel feedstock. 
     
     
         24 . The process of  claim 23 , wherein the at least one of sludge or solids are dried and used for the production of algae protein rich animal feed ingredient. 
     
     
         25 . The process of  claim 24 , wherein the clean mid-stillage is sent to a secondary evaporation system to further reduce the clean mid-stillage, wherein product from the secondary evaporation system is further recovered and dried for use as an animal feed ingredient.