When grain is harvested in Kentucky at moisture contents exceeding 13 to 14 percent, it must be dried to insure long-term safe storage. The drier the stored grain, the longer it will retain its quality

Bridges, Thomas C.

Fehr, Robert L.

Loewer, Otto J.

White, G. M.

English

University of Kentucky

University of KentuckyUKnowledgeAgricultural Engineering Energy Series Biosystems and Agricultural Engineering10-1978Energy in the Home: Grain Drying PerformanceEvaluationOtto J. LoewerUniversity of KentuckyThomas C. BridgesUniversity of Kentucky, tom.bridges2@uky.eduG. M. WhiteUniversity of KentuckyRobert L. FehrUniversity of Kentucky, robert.fehr@uky.eduRight click to open a feedback form in a new tab to let us know how this document benefits you.Follow this and additional works at: https://uknowledge.uky.edu/aees_reportsPart of the Bioresource and Agricultural Engineering CommonsThis Report is brought to you for free and open access by the Biosystems and Agricultural Engineering at UKnowledge. It has been accepted forinclusion in Agricultural Engineering Energy Series by an authorized administrator of UKnowledge. For more information, please contactUKnowledge@lsv.uky.edu.Repository CitationLoewer, Otto J.; Bridges, Thomas C.; White, G. M.; and Fehr, Robert L., "Energy in the Home: Grain Drying Performance Evaluation"(1978). Agricultural Engineering Energy Series. 33.https://uknowledge.uky.edu/aees_reports/33AEEII-7 GRAIN DRYING PERFORMANCE EVALUATION Otto J. Loewer, T. C. Bridges, G. M. White, and Robert L. Fehr UNIVERSITY of KE:IIITUCKY COLLEGE of AGRICULTURE DEPT. of AGRIC. ENGINEIERIIIIG COOPERATIVE EXTEI\ISIOIII SERVICE in cooperation will! KENTUCKY DEPARTMENT of ENERGY GRAIN DRYING PERFORMANCE EVALUATION Otto 1. Loewer, T. C. Bridges, G. M. White and Robert L. Fehr When grain is harvested in Kentucky at moisture contents exceeding 13 to 14 percent, it must be dried to insure long-term safe storage. The drier the stored grain, the longer it will retain its quality. The time required to dry corn or milo depends on several factors, including: air flow rate, drying air temperature and the quantity of moisture to be removed. Tentative investigations have indicated that if corn is above 18 percent moisture and 55°F for 24 to 48 hours, aflatoxin may develop, so this should also be considered when evaluating the performance of a grain dryer. You may estimate how your grain dcying system is performing by completing the following form and returning it to: Dr. Otto 1. Loewer Agricultural Engineering Department University of Kentucky Lexington, KY 40506 1.l I I I I I I I I I I I I I I I I I I I I 2.11 I I I I I I I I I I I I I I I I I I I II I I I I I I I I I I I I I I I I I I I NAME ADDRESS II I I I I I I I I I I I I I I I I I I I 3.1 I I 1-1 I I H I I I I PHONE NUMBER 4.1 I I I I 5.1 I I I I I 6.1 I I I I I TYPE OF GRAIN TO BE DRIED (com or milo only) TEMPERATURE OF AIR ENTERING GRAIN, °F Typical values are: a) Low temperature drying: 5 to 7°F above outside air temperature b) Layer dcying: I 0 to 20°F above outside air temperature c) Batch-in-bin dcying: 125 to 145°F d) Portable batch or continuous flow dcying: 180 to 220°F CUBIC FEET PER MINUTE OF AIR SUPPLIED TO EACH BUSHEL OF GRAIN IN THE DRYING SYSTEM Typical values are: a) Layer dcying or low temperature dcying: I to 3 CFM/BU b) Batch-in-bin drying: 8 to 12 CFM/BU c) Continuous flow or portable batch dcying: 75 to 125 CFM/BU Check your manufacturer's litera~ure for fan or drying performance data. You may also wish to use one of the University of Kentucky fan selection programs to assist you. 4 1.1 I I I I I I PERCENT MOISTURE CONTENT OF GRAIN AT HARVEST OR BEFORE DRYING BEGINS. 8.1 I I I I I I DESIRED FINAL PERCENTAGE MOISTURE CONTENT OF GRAIN AFTER DRYING. A sample computer analysis is shown below followed by a listing of terms. CORNoMILOoOR STOP (?CORN}- I FLClt~ t3 c6 r7 DF) (!. 0, 0 CFN/BI..i) %Wll) (c'iO.O F)-8 (O.OO~'iO HO) (0,0:1"'?) HM;\X) MO I ::;Tt.JF(E TEr··1PEP<"'< TUF:E ct.lJ'it)-9 2. :'520 4.640 (MIN )10 ( ~<'JE}II ( Mt<X }13 ( •'i'JFTI4 6.960 9.280 11.600 1."7 ~ 27 13 .. 78 :1.1 .~.)~) 9 .. 9~:; 2:.3.07 22,.26 20.47 :1. B. ~58 13.920 7.86 14.79 (Hl07. BTU/U< WATER}I7 1. CORN-Type of grain to be dried (Question 4). ;•;~;:· .· '') ~:...J + Ci~ lOB., 0 :l~?El .. O 1.~:):3.3 :1.:3~i + 3 24 .. 40 :t::-::6.4 2.1 .. 57 .137.:1. Co.on HU/I··IR·+nf-18 2. TEMP-Temperature of the drying air, °F, (Question 5). ··:>r.:· 1::· / ,.J + , __ 1 B7 .. 0 ?4 + [~ :1.0 :t + (J 107.9 1.13.{} 3. CFM/BU-The cubic feet of heated air delivered to each bushel of grain in the dryer (Question 6). 4. WBO-Percentage moisture content of the grain before drying begins (Question 7). 5. WBF-Desired average percent moisture content of grain after drying (Question 8). 6. HO-Absolute humidity of air, lb of water per lb of dry air. 7. HMAX-Absolute humidity of the drying air as it exits the grain. 8. 50°F~Assumed outside air temperature before the air is heated. 9. TIME- The lst column is time in hours from when drying begins. 74.1 74.3 74. :=s 81 .B .. :·. ··x ··x ... , , __ , • •. 1 + ,_, "-· -_?:~_; + :1.4 BO. 9~-~ B4 .. 0B B~=_; .. 9B B!5 • .16 10. MIN-The percent moisture content of the grain next to where the drying air enters the grain mass for specified times. 11. AVE-The average percent moisture content in the grain for specified times. 12. MAX-The percent moisture content of the grain where the drying air exits the grain mass for specified times. 13. MAX-The temperature of the grain next to where the drying air enters the grain mass for given times. 14. AVE-The average temperature of the grain for given times. 15. MIN~ The temperature of the grain where the drying air exits the grain mass for given times. 16. EFF~ The efficiency of the drying air in removing the moisture in the grain o~er given drying times. 17. BTU/LB WATER-The heat in BTU's required to heat the drying air divided by the amount of water in pounds that was removed fr()m the grain. 18. BU/HR-FT2 - This is the bushels dried per hour for each square ft of dryer's surface area for each 1.25 ft of grain depth. 5 ESTIMATING ENERGY USAGE: a. L.P. gas or natural gas The quantity of water removed from each bushel of grain may be calculated using the following equation: (lb of water) = removed (bulk density of) grain, lb/bu x (IM- FM) 100 · FM where IM =the initial moisture content of the grain before it was dried,%. FM = the final moisture content of the grain after it was dried, %. The bulk density of corn and milo is 56 pounds per busheL The amount of energy used per bushel for heating the air is: {BTU's per bu) = (f1;~~~~:;;1ter) x (lb of water removed) The total energy used for heating the air is found by (Total BTU's) =(BTU's per bu) x (total bu dried) It may be converted to gallons of LP gas or 1000 cubic feet of natural gas from the following relationships: I gal of L.P. gas= 92,000 BTU 1000 cubic ft of Natural Gas= 1,000,000 BTU The combustion efficiency of each fuel is approximately 80%. To illustrate how the energy usage and cost might be estimated, suppose a farmer has 30,000 bu. of corn he wishes to dry from 25 percent to 14.79 percent moisture content in a 24ft bin with 4 ft of grain. He uses L.P. gas at a cost of $050 per gallon. His operating conditions are the same as those presented with the sample output; that is, the drying air tempera~ lure is 140°F and 10 CFM per bushel is supplied by a I 0 hp fan. This would be very typical of a batch-in-bin drying system. To determine energy usage, the amount of water to be removed would be calculated: lb of water (removed ) per bushel lb 25. 14.79 = (56b,J x (100 _ 14_79) = 6.7llb/bu The energy to heat the drying air would be computed: 1807 BTU/lb (BTU'sperbu)=([Item 171 )x(6.7llb/bu)= 12,125 BTU/bu The total energy for heating the air to dry the grain is (BTU's, total)= {30,000 bu) x (12,125 BTU/BU) = 363,750,000 BTU Tilis is converted to gallons of L.P. gas assuming a burning efficiency of 80 percent: 363,750,000 BTU (L.P. gas, gallons)= (9l,OOO BTU/gal) x (O.S) = 4942 gal The cost would be $2471 or 8.24¢ per busheL b. Fan Energy The fan energy may be estimated using one of the other programs available. However, if it is assumed that for the example problem 10 hp is required to deliver the air through the grain at 10 CFM per bushel, the energy requirements would be Fan Energy .hours of (KWh ) ~ L t. ) x {fan horsepower) - r opera wn where 1000 watts~ 1 hp-hr when the efficiency of the motor is taken into account. The area of the drying floor is: (Square ft of dryer floor)= 3.1416 x (BIN DIAMETER)2 /4 = 3.1416 x (24)2 /4 = 452 ft 2 6 From the analysis, the drying rate is 0.073 bu per hour per 1.25 ft of grain depth for each square ft. of dryer surface area (Item 18). Therefore, the total time required to dry the grain is: al d . . ~e dried) x I 25 ft (tot rymg time)= h .f 2 Crain depth) (drying surface) r t X . b' X tn tn area 30,000 bu x 1.25 ft = 284 hr ,0.073 bu) (4 ft) (452 ft2) 'hr·ft2 X X The drying time could also be estimated by detemaining how many batches would be dried and multiplying this factor by the time required for each batch. For example: No. of batches (in batch-in-bin)= total bu to be dried system fl b D th f ( oar area ) x (O .8 ....'!.) x ( ep o) of bm, ft 2 ft 3 gram, ft 30,000 bu = (452 ft2) X (0.8 bu/ft 3) X 4ft = 20.74 batches (Total hours to) =(hours per ) x (No of batches) dry the grain batch (Item 9) = (13.92 hr) x (20.74 batches) = 289 hr The difference in the answers using the two approaches is because of round-off error. The drying rate is bu I (hr-ft2 -1.25 ft), the inverse of drying time; that is, (1/13.92) = 0.0718 rather than 0.073, the value given in Item 18. If we use the drying time figure of289 hours, the electrical energy consumption estimate would be: (i~.;rnergy) (289 hr) x (10 hp) = 2890 KW-hr If electricity may be purchased for 3.5¢/KW-hr, the electrical cost for drying would be approximately $101 or 0.34¢ per busheL To this figure, we would have to add the cost of fan operation time for cooling the grain, typically 2 hr per batch or for this example, an additional42 hr. AVAILABLE PROGRAMS: 1. BNDZN: Computer analysis of economics, energy consumption and engineering design for a grain storage system. 2. CHASE: Computer model that evaluates and compares costs of selected methods of harvesting, handling, drying and storage of com for an individual farmstead. Energy consumption is also estimated. 3. CACHE: Computer model for economic analysis of farm drying and processing systems. 4. SQUASH: Computer simulation of the harvesting-delivery-drying system used to detemaine bottlenecks in the System. *5. ESTIMATING FAN SIZES FOR GRAIN DRYING SYSTEMS *6. GRAIN DRYING PERFORMANCE EVALUATION *7. DRYERATION PERFORMANCE EVALUATION *8. NATURAL AIR-LOW TEMPERATURE DRYING PERFORMANCE EVALUATION *9. FAN PERFORMANCE ON GRAIN DRYING BINS ACKNOWLEDGEMENTS: *These programs were developed by: Dr. Thomas L. Thompson, Professor Agricultural Engineering Department University of Nebraska Lincoln, Nebraska The College of Agriculture is an Equal Opportunity Organization with respect to education and employment and is authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, national origin, sex. religion, age and handicap. Inquiries regarding compliance with Title VI and Title VII of the Civil Rights Act of 1964, Title IX of the Educational Amendments. Section 504 of the Rehabilitation Act and other related matters should be directed to Equal Opportunity Office, College of Agriculture. University of Kentucky, Room S-105. Agricultural Science Building-North, Lexington. Kentucky40546 Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914. in cooperation with the U.S. Department of Agriculture. Charles E Barnhart, Director of Cooperative Extension Service. University of Kentucky College of Agriculture, Lexington, and Kentucky Stale University, Frankfort. 3M-10-78; rev. 3M-2-81 

Energy in the Home: Grain Drying Performance Evaluation

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Energy in the Home: Grain Drying Performance Evaluation

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