FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA " SECTION FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA 93 CARD Project FLAT-BED DRYER Sub-Component 2006/2007 Report Reporting period: from 15 May 2006 to 28 Feb 2007 Compiled by: Phan Hieu Hien, Ph.D with contributions from staff of the NLU Center for Agricultural Energy and Machinery: Le Quang Vinh, Tran Thi Thanh Thuy, Tran Van Tuan, Nguyen Thanh Nghi March 2007 94 CONTENTS CARD PROJECT, FLAT-BED DRYER SUB-COMPONENT 2006 REPORT 96 INTRODUCTION 96 INSTALLATION OF THE 8-TON FLAT-BED DRYER 96 EXPERIMENTS WITH THE 8-TON DRYER UNDER ACTUAL PRODUCTION CONDITIONS 98 3.1 Objectives .98 3.2 Materials and methods 98 3.3 Results and discussion: .98 3.3.1 July 2006 experiments .98 3.3.2 March 2007 experiments 98 FABRICATION OF A LAB (MINI) DRYER FOR EXPERIMENTING UNDER CONTROLLED CONDITIONS .99 4.1 Objective 99 4.2 Materials and methods 99 4.3 Results and discussion (1-to dryer) 104 THE PRRA SURVEY ON THE USE OF FLAT-BED DRYER AND THE COST OF VARIOUS DRYING METHODS IN THE MEKONG DELTA .110 5.1 Background 110 5.2 Objectives .110 5.3 Method 110 5.4 Result and discussion 110 5.4.1 Background data 110 5.4.2 Post-harvest and drying status .112 5.4.3 Conclusions 114 EXTENSION MATERIALS FOR TRAINING COURSES, BASED ON THE OUTCOME OF THE SURVEY AND EXPERIMENTS 115 CONCLUSIONS AND FURTHER PROPOSALS 116 EVALUATION OF FARMERS’ PRACTICE .117 8.1 Value losses due to field drying and sun drying 117 REFERENCES 118 10 APPENDIX 119 10.1 Appendix : Paddy milling quality analysis (procedure by IRRI) 119 95 CARD Project, FLAT-BED DRYER Sub-Component 2006 Report (from 15 May 2006 to 28 February 2007) INTRODUCTION The sub-component of CARD Project 026/VIE-05 on the flat-bed dryer study, as specified in the contract, consists of the following activities: • Select the site and supervise the installation of an 8-ton flat-bed dryer for experiments • Conduct experiments with the 8-ton dryer under actual production conditions • Build a lab (mini) dryer and other needed tool for experimenting under controlled conditions • Conduct experiments to determine the optimum drying conditions for the flat-bed dryer (with or without air reversal) using the lab mini-dryer at the Nong-Lam University or a nearby location • Conduct a Participatory Rapid Rural Appraisal (PRRA) survey on the use of flat-bed dryer in the Mekong Delta • Write extension materials for future training courses, based on the outcome of the survey and experiments The above activities can be clustered into groups: - The 8-ton dryer - The 1-ton dryer - Survey, training, and extension This is the final report of the above-mentioned activities, covering the period from 15 May 2006 to 28 Feb 2007 It is compiled from earlier Progress Reports, and updated with most recent data and findings, thus conclusions from this report supercede the earlier reports for any discrepancies INSTALLATION OF THE 8-TON FLAT-BED DRYER Together with the Project Leader, Dr Truong Vinh, we selected the site for installing the 8-ton flat-bed dryer; the site was Tan-Phat-A Cooperative, located in Tan-Hiep District, Kien Giang Province At first, we intended to contract from a local dryer builder for a typical dryer in the region, adding features needed for the experiment, but no contractor was willing to meet the needs they considered too time-consuming with these added features in a miscellaneous contract for their business So, the research team decided to build an 8-ton air-reversible dryer which is a SRA-8 design from NLU with slight modifications The installation of the dryer was completed in mid-July 2006 (Fig.1 & 2), just in time for the wet-season harvest and for experimental purposes 96 Figure 1: The 8-ton dryer at Tan-Phat-A Cooperative, Kien Giang Figure 2: The 8-ton dryer with the air for downward direction 97 EXPERIMENTS WITH THE 8-TON DRYER UNDER ACTUAL PRODUCTION CONDITIONS 3.1 Objectives To determine the performance of the dryer under actual production conditions, for different drying regimes 3.2 Materials and methods The experiments were conducted in July 2006 Tan-Phat-A Cooperative, Tan-Hiep District, Kien-Giang Province Eight experiments were done, with factors under study • Air reversal at levels: a) YES , and • Drying temperature at levels: a) Constant at 43 oC ; and b) At 50 oC for the first hour, and afterwards constant at 43 oC In reality, due to the furnace configuration, the temperature rarely exceeded 50 oC, and was about 48 oC at most b) NO Each treatment was replicated twice However, due to severe difficulty in securing batches of the same quantity or initial moisture content, the experiments were not strictly factorial The arrangement of factor levels is for systematic observation only Due to different views on milling analysis, data on head rice recovery were discarded Thus in March 2007, another set of experiment was replicated, with focus on comparing the crack and head rice recovery of different drying modes, namely with and without air reversal Sun drying on the cement drying yard with a 7-cm paddy layer, as popularly practiced by local farmers, was replicated as control treatment The crack analysis was done at the VINACONTROL, an accredited agency in charge of certifying the rice quality for export Each treatment was analyzed by samples, each consisting of 30 grains taken at random; each paddy grain was hand-husked and examined under the magnifying glass for fissure The head rice recovery analysis was done at the Rice Quality Laboratory of the NLU Chemical Technology Department, following procedures adopted by International Rice Research Institute (see Appendix) and the University of Queensland 3.3 Results and discussion: 3.3.1 July 2006 experiments The experiment results are summarized in Table Figures and show the moisture reduction curves Remarks: - The effect of air reversal is very apparent in reducing the final moisture differential When operated correctly, this differential is less than % with air reversal, but at least 5% without air reversal More MC differential means more rice cracking during milling This explains why dryers installed since 2003 have been more and more of the reversible principle - Air reversal also decreased the drying time - The drying temperature is stable and can be kept within ± oC 3.3.2 March 2007 experiments Results are in Table All above observations hold with these new experiments Data on the crack of rice upon milling show that: 98 a) Mechanical drying, whether with or without air reversal, is superior to sun drying in terms of less crack percentage or more head rice recovery About 3- % less cracking, and about % more head rice recovery are main data obtained from this set of experiments b) Mechanical drying with air reversal resulted in less Final MC differential (2.2 %) compared to without air reversal (4.6 %) c) The increase in crack percentage between mechanical drying with and without air differed by only %; while judged by the head rice recovery, the difference was only 0.4 %, or almost no difference (Table 2) This was not expected in line with the above data on Final MC differential Thus more experiments should be conducted in the future to confirm the trend FABRICATION OF A LAB (MINI) DRYER FOR EXPERIMENTING UNDER CONTROLLED CONDITIONS 4.1 Objective To determine the performance of the 1-ton dryer under controlled conditions 4.2 Materials and methods A lab mini-dryer of maximum capacity of ton was designed and fabricated for experimenting under controlled conditions (Fig.5) (a) (b) Figure 5: The 1-to dryer: Airflow upward; (b) Downward reverse airflow 99 Table 1: Summary of drying batches (July 2006 ) 2523-7 25-7 Date /2006 26/7 30-7 24-7 27-7 23-7 29-7 Batch Number Temperature, oC 43 43 43 43 48 x43 48 x43 48 x43 48 x43 Air reversal Yes Yes No No Yes Yes No No Drying time, h+xx/100 10.42 6.00 10.50 8.75 10.00 3.58 5.75 11.67 Air reversal time, minute 10 15 - - 15 10 - - - - 60 - - - - Break-down time, minute Ave Initial MC, % 27.4 19.3 21.5 24.5 25.6 20.7 25.6 26.0 Final MC: Bottom, Max: 9.1 13.9 11.7 13.2 13.4 14.1 8.1 12.8 Final MC: Bottom, Min: 5.9 12.1 11.2 11.2 12.2 13.1 6.1 10.6 Final MC: Bottom, Ave,%: 8.2 13.4 11.6 12.0 12.7 13.6 7.6 11.3 Final MC: Top, Max: 15.5 14.9 23.1 22.7 17.3 15.2 13.0 22.6 Final MC: Top, Min: 15.2 13.3 15.2 15.5 15.8 14.4 12.2 17.8 Final MC: Top, Ave, %: 15.3 14.2 18.9 19.1 16.5 14.8 12.5 20.4 7.1 0.8 7.3 7.1 3.8 1.2 4.9 9.1 10.13 9.72 10.23 9.62 10.23 9.78 9.78 9.71 0.28 0.22 0.16 0.17 0.16 0.22 0.15 0.20 5.31 5.10 5.37 5.05 5.37 5.13 5.13 5.10 5.19 42.8 42.5 43.3 41.4 42.2 44.8 42.2 44.3 42.9 2.0 2.8 2.4 2.8 3.6 2.8 3.6 3.2 2.9 16.2 16.25 12.41 12.14 12.0 11.83 12.0 12.20 13.1 Bulk density:Before, kg/m 521 505 529 495 529 525 522 523 519 After drying, kg/m3 480 484 465 493 498 515 477 503 489 Paddy : BEFORE, kg 8338 7246 8185 7860 8805 8724 5307 9438 AFTER drying, kg 6946 6564 - 7368 7462 7706 4599 8307 Grain depth: BEFORE, m 0.508 0.456 0.491 0.504 0.528 0.528 0.323 0.573 AFTER drying, m 0.459 0.431 - 0.474 0.475 0.475 0.306 0.524 416.4 206.4 220.9 282.2 371.5 138.9 160.5 373.0 39.95 34.40 21.04 36.41 37.16 38.80 27.92 31.96 18.0 17.0 16.6 12.0 17.00 6.0 9.50 17.0 1.73 2.83 1.58 1.55 1.70 1.68 1.65 1.46 Final MC differential, % Air SUPERFICIAL Velocity Average , m /minute ± Std Dev., m /minute AIR FLOW, m3/s Av Drying temp, oC ± Std.Dev, oC Temp Increase, oC Husk consumption: Total, kg kg/ hour Diesel consump :Total, Lit Lit/ hour 9.90 33.45 1.77 100 Table 2: SUMMARY results of March 2007 experiments: Comparison of drying batches Batch (46+43 oC, with air reversal) Batch (46 x43 oC, WITHOUT air reversal) (46 x43 = 46 oC in first 1,5 hours, &43 oC in remaining time) Place Tan Phat A Cooperative, Ken Giang Province Date: March 2007 Batch Number Batch Batch Air reversal Yes Drying temperature (oC) ± StDev No 43.3 ± 3.1 43.0 START date-time 08-03-07 10:30 10-03-07 11:30 END date-time 08-03-07 16:30 10-03-07 17:30 6.00 6.00 Drying time, h+xx/100 Air reversal time, minute ± 2.9 15 Laborer for air reversal Initial MC, % (Ave ± StDev) 23.86 Final MC % (Ave ± StDev) 14.94 ± 0.71 20.41 ± 0.45 16.07 Top layer 13.92 0.31 18.23 0.75 Middle layer 16.16 1.05 16.38 0.7 Bottom layer 14.75 0.63 13.59 0.47 MC differential Top-Bottom, % MC differential Middle-Top , % 0.83 4.64 2.24 AIRFLOW (20 points) Airflow, m3/s 5.88 Superf vel (Ave ±StDev), m/min 11.20 5.70 ± 0.30 10.85 Rice husk consumption: kg /batch 171.2 215.2 Rice husk consumption: kg / hr 28.5 35.9 Diesel consumption, liter /h 1.70 1.75 Initial Paddy mass, kg 9276 9197 Initial Paddy Layer (Ave±StDev), mm 517.8 15.6 507.8 ± 0.37 7.5 Crack BEFORE drying, % 12.00 Differ 21.00 Differ Crack AFTER drying, % 13.75 1.75 23.75 2.75 Crack, Sun drying on Cement yard, 7-cm layer, % 17.80 5.80 26.80 5.80 Head Rice Recovery, % Head Rice %, BEFORE drying 62.72 Differ 59.12 Differ Head Rice %, AFTER drying 59.39 -3.33 56.21 -2.91 Head Rice %, Sun drying 55.58 -7.14 52.12 -7.00 Difference (Sun & Mechanical) % -3.81 -4.09 101