Patent Publication Number: US-7910341-B1

Title: Process for harvesting and processing sugar-producing crops

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to U.S. patent application Ser. No. 10/429,091 filed May 2, 2003 entitled FIELD HARVESTER FOR SWEET SORGHUM. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a method of harvesting and processing sugar-producing crops such as sweet sorghum. More particularly the present invention relates to a process for cutting and processing sweet sorghum in the field to yield its juices, and then to further process the juice via fermentation and distillation to produce ethanol. 
     2. Background Art 
     Traditionally, sweet sorghum has been harvested for sorghum syrup production by either cutting and handling the stalks by hand, or by chopping the stalks and blowing the chop into a forage wagon; in either case, the resulting plant matter is carried to a central processing station for the extraction of the juices, cooking and reduction of the juices to sorghum syrup. 
     The former method requires a large expenditure of manual labor and is typically used in small, such as family sized operations. The juice from the stalks is often squeezed using a single-roller press powered by a horse, mule, or lawn tractor. 
     The method of chopping the stalks in the field like ensilage is less labor intensive than the previously mentioned method and larger crops may be harvested and processed this way. The drawbacks of this method, however, include: an enormous amount of crop must be transported out of the field to a central processing location, and the resultant organic matter must then be either returned to the field or otherwise disposed of. 
     Energy is a matter of concern to the country, and will continue to be for some time. Air pollution has improved over the past several decades, but still remains an issue in parts of this country, as well. A recognized partial solution to both the energy and pollution problems is ethanol. Sweet sorghum juice, due to its high sugar content, is an ideal raw material for the production of ethanol. Sweet sorghum has the potential to produce over twice the ethanol per acre as corn, the most common raw material used for ethanol production, today, at significantly less cost. As it stands presently, a more efficient method of harvesting of the sorghum crop must be employed to make the use of this crop for ethanol production feasible. 
     There is, therefore, a need for a low-labor, efficient process for harvesting and field processing sweet sorghum and extracting the juices for further processing at or near the fields of each producer. 
     SUMMARY OF THE INVENTION 
     A purpose of this invention is to provide a process for field harvesting and processing sweet sorghum crops and extracting the juices for further processing elsewhere. Another purpose of this invention is to provide a process for fermenting sugar rich substances such as sweet sorghum juice, ultimately for its ethanol. Still another purpose is to provide a portable process for distilling the ethanol from the wine. 
     A field harvesting process for sweet sorghum is initiated by cutting the stalks of the sweet sorghum close to the ground. The crop is then fed into a multiple roller press, for the extraction of the juices from the cane stalks. The roller press incorporates multiple rollers under high pressure. A screw press is used to maximize the sugar extraction from the spent cane stalks or bagasse. 
     A continuous belt filtering process removes solids from the juices while returning the resulting solid matter for further processing by roller pressing and screw pressing to remove all the potential juices and, subsequently, to be made into a marketable product such as pellets to be used as livestock feed, fuel or other products. 
     If necessary, the pH of the juices will be adjusted (by the addition of acid) as it travels through the field harvester to reduce bacterial action in the juice. Depending on the operation and desired end product, yeast may be added to the juice within the field harvester as well. 
     A temporary storage tank, either on board the field harvester or pulled behind or to the side, holds the produced juices. From the field harvester, the juices are transported out of the field to nearby storage and subsequent processing. The juices may be converted to syrup, ethanol, lactic acid or other products. 
     The present invention includes a fermentation process, which takes place within the storage units in a matter of days, and a portable distillation process to recover the ethanol from the resultant wine and to concentrate this ethanol to fuel ethanol. Tanks for storage and fermentation may take many forms. Stationary, rigid tanks may be used, but portable bladders provide a less expensive and more flexible alternative. In either case, a vent for permitting the release of Carbon Dioxide (CO 2 ) gas is necessary during the fermentation process. 
     A portable distillation process, mounted on a “low-boy” type truck or semi trailer, concentrates the ethanol to a fuel level. The distillation process may use fossil fuel(s) for the heat required, but an aspect of the present invention is to gasify the solid crop material or bagasse for the heat needed for distillation. 
     A distillation process comprises:
         a heating unit in which the fermented juices (wine) are heated so the alcohol will evaporate at about 180° F.;   a condensing unit in which the alcohol is cooled so it condenses; and   a molecular sieve unit in which distilled alcohol is concentrated to fuel grade.
 
Strict quality control measures must be taken at this point in the overall process due to the requirement that the alcohol be of fuel grade.
       

     The novel features which are believed to be characteristic of this invention, both as to its organization and method of operation together with further objectives and advantages thereto, will be better understood from the following description considered in connection with accompanying drawings in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood however, that the drawings are for the purpose of illustration and description only and not intended as a definition of the limits of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a flow diagram of a sweet sorghum field harvesting process. 
         FIG. 2   a  is a plan view of a roller press unit for removal of sugar-laden juice from cane stalk. 
         FIG. 2   b  is a side elevation view of a roller press unit for removal of sugar-laden juice from cane stalk. 
         FIG. 2   c  is a frontal elevation view of a roller press unit for removal of sugar-laden juice from cane stalk. 
         FIG. 3   a  shows a single screw press for further removal of sugar-laden juice from cane stalk. 
         FIG. 3   b  shows a double screw press for further removal of sugar-laden juice from cane stalk. 
         FIG. 4  shows an endless belt filter press unit. 
         FIG. 5  shows a layout of a sweet sorghum harvester. 
         FIG. 6  shows a typical distillation process. 
         FIG. 7  shows the distillation process unit mounted on a semi-trailer. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A flow diagram for a mobile sweet sorghum field harvesting process is shown in  FIG. 1 . At the top, the sweet sorghum crop  100 , mature for harvest, is harvested by a field harvester  580  (see  FIG. 5 ). The cutting and feeding step  110  implies cutting the crop off near the ground and feeding it into a pressing process  115  (a multiple roller press) for the primary step in separating the juices from the solids. The extracted juices are passed to an endless belt filter press process  120 , where the solids are strained out of the juice. From the endless belt filter press process  120 , a filter cake is obtained and returned via a conveyance  125  that returns the cake to the multiple roller pressing process  115  for additional juice extraction. The solids (bagasse) from the multiple roller pressing process  115  may be:
         1. expelled back to the field;   2. passed to a screw press process  130  where the last of the available juice to be extracted is removed; or   3. a combination of 1 and 2.       

     The juices from the latter stages of the multiple roller pressing process  115  are cycled forward at each stage of the multiple roller pressing process  115  by feed-forward pumps  132  to wash and help extract more of the sugars from the solids. The cleaned and filtered juices are then pumped from the endless belt filter press process  120  to an on-board nanofiltration membrane process  142  for partial removal of excess water and consequent increased concentration of the sugars. The water removed in the nanofiltration membrane process  142  is used as belt filter wash water and to replenish the wash tank  540 . Excess water is expelled to the field. Eventually, all the juices pass to an optional pH adjustment  135  where the pH is measured and adjusted to about 4.5-4.8 to inhibit bacterial action. If the final product is to be lactic acid or some other products, this step may be unnecessary. The juices then continue to an on-board or trail-behind storage tank  140  for temporary storage until the juices are removed and transported to nearby larger storage/fermentation tanks for fermentation and subsequent distillation in a final processing step  145 . 
     Simultaneously, the solids leaving the screw press process  130  may be made into pellets in a rotary ring pelletizing process  150  and transported to storage  155 . These pellets may be used for fuel for alcohol distillation, for livestock feed or for other purposes. The solids may instead be converted into other, marketable products. 
     The physical unit for the multiple roller press process  115  is shown in  FIG. 2 . The heavy side rails  200  of the frame support multiple rollers  210  whose purpose is to squeeze the juice from the stalks of the crop. The rollers  210  have optional grooves machined into them and are hung on double roller bearings at each end. Spacing between the side rails  200  is maintained by tie beams  220 . Force is applied downward to each roller in the top layer of rollers  210  by hydraulic cylinders  230 . 
     A screw press unit for the screw pressing process  130  is used to maximize the production of juice from the sweet sorghum crop. Typical examples are shown in  FIG. 3 , but this invention is not limited to any particular design of screw press unit. In  FIG. 3   a  a single screw press extruder  130   a  is shown, while in  FIG. 3   b  a double screw press  130   b  is shown. 
     From the multiple roller pressing process  115  and the screw pressing process  130 , the extracted juices with entrained solids (slurry) pass to the endless belt filter press process  120  shown in  FIG. 4 . Again, the present invention is not limited to a particular endless belt filter unit design. As the name implies, the endless belt filter press unit comprises two endless belts  400 ,  405  routed around a series of rollers  410 . The belts run close to one another over part of their length  420  to compress and remove the entrained solids from the juices. This compression accomplishes two effects:
         1. The squeezing of much of the juice from the solids.   2. The forming of a press cake  440  to be returned to the multiple roller press unit  115  for further juice extraction.
 
This press cake  440  is conveyed back to the multiple roller press  115  by the press cake return conveyor  125 , where more of the juice is pressed out of the solids.
       

     A water nozzle  430  sprays the filter belt  400  with water to clean the belt so it can be used continually during the harvest session without requiring periodic cleaning. 
     An example of how a sweet sorghum field harvester  580  may be laid out is shown in  FIG. 5 . The field harvester  580  is powered by an engine  500 , preferably diesel. The harvester is operated from a cab  510 . The cutting and feeding unit  110  is carried on the front of the field harvester  580  where the crop is sheared from the ground and transferred to the multiple roller press process  115  near the cab  510 . The endless belt filter press process  120  is beneath the multiple roller press  115 . Feed-forward pumps  132  are close to the multiple roller press unit. Transfer and wash pumps  520  are in close association with the endless belt filter press process  120  as it transfers the clean juice from the endless belt filter press process  120  to the nanofiltration membrane process  142 . From there, a pH adjustment of the juices is carried out, if necessary before or as the juices are pumped to the storage tank  140 . A tank for acid  530  for adjusting the pH of the juice to about 4.5-4.8 is carried a water tank  540 . Yeast may also be introduced on board the harvester  580 . Water, for washing the endless belt  400 , is contained in a tank  540 . 
     The solids, or bagasse, continue from the multiple roller press process  115  to the screw press process  130 , and then, optionally, to a pelletizing process  150  to form them into pellets useful for feed, fuel or other products. 
     The sweet sorghum field harvester  580  need not be a self-propelled machine as indicated in  FIG. 5 . A sweet sorghum field harvester  580  that is made to be pulled behind a tractor or other vehicle, and powered via a power takeoff shaft or other means is a viable alternative and may be attractive for smaller operations. In any case, the sweet sorghum field harvester is mobile, that is, not stationary. 
     The field harvesting process described above may be used for any sugar-containing crop including sweet sorghum and sugar cane. 
     After the sweet sorghum crop has been processed into its juices in the sweet sorghum field harvester  580 , the juices must be further processed into a useable and saleable product. Thus, other aspects to the present invention are further storage and processing  145  comprising:
         1. fermentation tanks  605  as shown in  FIG. 6 ; and   2. a portable distilling process  700  as illustrated in  FIG. 7 .
 
Thus, sweet sorghum juices from the field harvester  580  are transferred into storage/fermentation tanks  605 . During this transfer from the field harvester  580  the selected yeasts are added, and the fermentation process begins and typically lasts for a few days. Throughout fermentation, CO 2  is produced. These fermentation tanks  605  may take many forms. A rigid, stationary tank would be suitable, however, a portable, fiber elastic bladder would be less expensive and more flexible. Irrespective of the form of the storage/fermentation tanks  605 , it must have a vent  610  for venting the CO 2  produced by the yeast during fermentation. The CO 2  may be captured for sale.
       

     The ethanol laden juices, called wine are transported or transferred from the storage/fermentation tanks  605  under gravity or with a wine pump  615  into a wine tank  620 . From the wine tank  620 , the wine is transported under gravity or by a distillation pump  625  into a distillation boiler/column  630 . In the distillation column  630 , the alcohol is separated from the remainder of the wine, or stillage. The resulting low-grade alcohol may be further cooled in a heat exchanger  635  used to preheat the wine before being further refined in a molecular sieve stripping unit  665 . This final product fuel ethanol is then loaded into a tank for storage or transport. 
     Heat for the distillation column is provided by heating water in a boiler  640 . The fuel  645  for the boiler may be Liquid Propane (LP), or other fossil fuel, or the bagasse (the solids left over after removing the juice from the sweet sorghum) may be put through the process of gasification, and the resulting fuel  645  burnt to heat the boiler  640 . 
     Gasification of a carbonaceous material such as bagasse results in a fuel referred to as producer gas. The combustible components are, largely, carbon monoxide (CO) and hydrogen (H 2 ). 
     Steam, from the boiler  640 , first travels to the distillation column  630 . From the distillation column  630 , the condensate is used in the wine tank  620  to preheat the wine before distillation. A wine tank heat exchanger  650  in the wine tank  620  imparts the heat to the wine. From the wine tank  620 , the condensate moves to a condensate holding tank  670 . The condensate is finally returned to the boiler through a boiler feed pump  660 . 
       FIG. 7  depicts an example of a portable part of the distillation process  600  (also inside the heavy dot-dashed line in  FIG. 6 ). In this case, the distillation column  630 , with its heat exchanger  635 , the boiler  640 , condensate holding tank  670 , the wine tank  620 , the molecular sieve stripping unit  665 , associated pumps  615 ,  625 , the boiler feed pump  660 , and associated controls are carried on a semi trailer  700 . Other combinations are possible. 
     The above embodiments are the preferred embodiments, but this invention is not limited thereto. Many of the elements of the process mentioned, above, are optional, providing for a large degree of flexibility and pricing. It is, therefore, apparent that many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.