Patent Publication Number: US-11376521-B2

Title: Efficient distillation of ethanol

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation-in-Part of and claims priority in U.S. patent application Ser. No. 16/260,686, filed Jan. 29, 2019, which claims priority in U.S. Provisional Patent Application No. 62/623,459, filed Jan. 29, 2018, all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention provides systems and methods for improved distillation of ethanol in or in conjunction with an ethanol plant. Ethanol may be produced by fermenting grains, cellulosic material, or other organic matter to produce a beer containing a relatively low percentage of ethanol in a mixture with water, various dissolved solids, and other materials. The distillation process may separate the ethanol, which may be useful for fuel, industrial, or other uses, from the other components of the beer. 
     2. Description of the Related Art 
     Ethanol may be produced by fermenting grains, cellulosic material, or other organic matter to produce a beer containing a relatively low percentage of ethanol in a mixture with water, various dissolved solids, and other materials. The distillation process may separate the ethanol, which may be useful for fuel, industrial, or other uses, from the other components of the beer. 
     Distilling ethanol consumes significant quantities of energy resources, which represent a major operating expense for ethanol distillation plants. Efficient plant operation tends to reduce such operating expenses, thus lowering the costs of ethanol end products. Operating costs can be reduced and efficiencies can be increased by maximizing the effective use of energy inputs. For example, heat generated in one operation can be utilized for driving other operations. Current plant designs typically vent or discharge substantial quantities of heat to the atmosphere. Capturing such waste energy can improve efficiencies and reduce operating expenses. 
     The present invention addresses such ethanol distillation plant efficiency objectives by providing a method and system for capturing heat from dryer exhausts, and using such captured heat for driving ethanol distillation plant operations. 
     Heretofore there has not been available a system or method for distillation of ethanol with the advantages and features of the present invention. 
     SUMMARY OF THE INVENTION 
     In practicing an aspect of the present invention, a dryer exhaust heat subsystem captures heat from a dryer and further heats a warm water stream in a scrubber, which outputs hot water to the ethanol plant. In the practice of the method of the present invention, captured dryer exhaust heat increases overall ethanol plant efficiencies by reducing the net energy input required for driving plant operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings constitute a part of this specification and include exemplary embodiments of the present invention illustrating various objects and features thereof. 
         FIG. 1  is a schematic representation of an ethanol distillation system with a dryer exhaust heat capture subsystem for improving system performance, embodying an aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     I. Introduction and Environment 
     As required, detailed aspects of the present invention are disclosed herein, however, it is to be understood that the disclosed aspects are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art how to variously employ the present invention in virtually any appropriately detailed structure. 
     Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, up, down, front, back, right, and left refer to the invention as orientated in the view being referred to. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the aspect being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of similar meaning. 
     II. Preferred Embodiment 
     Systems and methods in accordance with the present invention may receive beer  120  from an ethanol plant  50 . The beer  120  may contain between 12% wt and 15% wt ethanol and may be at a temperature between 140° F. and 160° F., although other percentages of ethanol content and other temperatures are possible in accordance with the present invention. 
     The beer  120  may be fed to the first distillation column, referred to as beer column  100 . Beer column  100  may be run at a temperature between 150° F. and 170° F. at the bottom of the column  100 . Beer column  100  may be driven by energy sources derived from integration with other components and systems of the plant  50 . For example, the main energy source for beer column  100  may come from vapors  570  from the fourth effect of the main evaporators  550 . An additional source of heat for beer column  100  may be from a reboiler  160  which condenses some of the steam vapors  420  from the vapor condensing system  400 , producing a condensate stream  170 , a portion of which can be returned to the ethanol plant  50  for reuse. 
     The stripped beer column bottoms  130  from the bottom of the beer column  100  may be sent to a centrifuge process  500  for further processing. The ethanol-rich vapors  140  produced by the beer column  100  may be condensed using a condenser  110 . Condenser  110  may be cooled using cooling tower water. Condenser  110  may be run at a very low pressure of between 0.5 psia and 4 psia. 
     Ethanol-laden condensate  150  produced by the condenser  110  may be pumped to a rectifier system  200  where the ethanol may be purified to 190 proof ethanol vapor  220 , for example, using either one or two columns that may be run in series. Steam  210  may be used to add heat to the rectifier system  200 . The column(s) of rectifier system  200  may be operated at high pressure, such as between 50 psig and 70 psig, with the 190 proof vapors  220  from the column may be split between feeding the dehydration system  300 , which may consist of molecular sieves or membrane technology, and being directly condensed using the vapor condensing system  400 . The condensate  225  from the vapors that are directly fed to the vapor condensing system  400  are collected and sent back to the rectifier  200  as reflux. 
     Water may be removed from the 190 proof vapors  220  in the dehydration system  300 . Dehydrated vapors  320 , which will be at  200  proof, may be received from the dehydration system  300  and may be condensed using a vapor condensing system  400 . The condensed  200  proof product  330  may be sent to the tank farm at the ethanol plant  50  for storage and load out. 
     The vapor condensing system  400  may be used to integrate the heat from the 190 proof vapors  220  directly received from the rectifier  200  and the  200  proof vapors  320  from the dehydration system  300  with other sections of the plant. The vapor condensing system  400  may condense the vapors and boil steam condensate to produce steam vapors  420 . The steam vapors  420  may be used to drive the first effect of the main evaporators  550  and evaporation of water at the rotary dryer  900 . The water phase  240  pulled from the bottom of the rectifier system  200  may be returned to the ethanol plant  50  for reuse. 
     The bottom stream  130  from the beer column  100  may first be sent to a centrifuge process  500  that may separate out most of the suspended solids into a solids cake  520 . The solids cake  520  may be between 30% wt and 40% wt solids. The resultant low solids centrate  530  may be sent to the main evaporators  550  to produce a syrup product  540  and evaporator condensate  560 , which may be returned to the ethanol plant  50  for reuse. 
     The syrup product  540  may be between 25% wt solids and 34% wt solids and may be sent to the corn oil extraction system  600  where product corn oil  620  may be removed from the syrup to produce a de-oiled syrup product  610 . Product corn oil  620  may be sent to the ethanol plant  50  for storage and load out. 
     The de-oiled syrup  610  may then be sent to the finish evaporators  800  where the syrup may be further concentrated to finished syrup  810  having between 38% wt and 74% wt solids. The evaporator condensate  840  from the finish evaporators  800  may be returned to the ethanol plant  50  for reuse. 
     The solids cake  520  from the centrifuge system  500  may be mixed with the finished syrup  810  from the finish evaporators  800  and then may be sent to a rotary dryer  900  and heated using steam vapors  420  from the vapor condensing system  400  to produce a distillers dried grains with solubles (DDGS) product  920 . This DDGS product  920  may be between 8% wt and 12% wt moisture and may be sent to another area of the ethanol plant  50  for storage and load out. 
     The distillers dried grains (DDG) dryer exhaust  940  may be diverted to a regenerative thermal oxidizer (RTO)  980  which removes organic impurities from the exhaust gas before the treated gas  955  is fed to a scrubber  950  where the dryer exhaust  940  may be contacted counter its current with a warm water stream  945 . This water stream may be heated to between 185° F. and 205° F. and may leave the bottom of the scrubber  950  as supply hot water  946 . The exhaust gas  955  may be vented from the top of the scrubber  950  to the atmosphere. 
     The supply hot water  946  produced by the scrubber  950  may be pumped to a hot water flash tank  965  located next to the main evaporators  550  where the water stream may be flashed to sending vapors  952  to the third effect of four effects, of the main evaporators  550 . The hot water return  954  leaving the bottom of the hot water flash tank  965  may then be pumped to the finish evaporators  800 , where the hot water may be used to transfer heat to the evaporator to vaporize water from the de-oiled syrup  610  to produce finished syrup  810 . The hot water return  954  may be cooled, producing warm water return  945  that may be sent back to the scrubber  950 . The evaporator condensate  840  from the finishing evaporators  800  may be returned to the ethanol plant  50  for reuse. 
     It is to be understood that the invention can be embodied in various forms and is not to be limited to the examples specifically discussed above. The range of components and configurations which can be utilized in the practice of the present invention is virtually unlimited.