FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA

FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA "LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com... SECTION 3 F

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FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA "

LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com

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SECTION 3

FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS

OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA

93

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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 Van Tuan,

March 2007

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CONTENTS

CARD PROJECT, FLAT-BED DRYER SUB-COMPONENT 2006 REPORT 96

1 INTRODUCTION 96

2 INSTALLATION OF THE 8-TON FLAT-BED DRYER 96

3 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

4 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

5 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

6 EXTENSION MATERIALS FOR TRAINING COURSES, BASED ON THE OUTCOME OF THE SURVEY AND EXPERIMENTS 115

7 CONCLUSIONS AND FURTHER PROPOSALS 116

8 EVALUATION OF FARMERS’ PRACTICE 117

8.1 Value losses due to field drying and sun drying 117

9 REFERENCES 118

10 APPENDIX 119

10.1 Appendix 1 : Paddy milling quality analysis (procedure by IRRI) 119

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CARD Project, FLAT-BED DRYER Sub-Component

2006 Report (from 15 May 2006 to 28 February 2007)

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 3 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 2 earlier Progress Reports, and updated with most recent data and findings, thus conclusions from this report supercede the earlier reports for any discrepancies

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

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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

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3 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 2 factors under study

• Air reversal at 2 levels: a) YES , and b) NO

• Drying temperature at 2 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

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 2 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 3 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:

The experiment results are summarized in Table 1 Figures 3 and 4 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 2 % 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 ± 3 oC

Results are in Table 2 All 3 above observations hold with these new experiments

Data on the crack of rice upon milling show that:

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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- 4 % less cracking, and about 4 % 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 1 %; 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

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 1 ton was designed and fabricated for experimenting under controlled conditions (Fig.5)

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Table 1: Summary of 8 drying batches (July 2006 )

48 x43

Air reversal time, minute 10 15 - - 15 10 - -

Break-down time, minute - - 60 - - - -

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: 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 differential, % 7.1 0.8 7.3 7.1 3.8 1.2 4.9 9.1 Air SUPERFICIAL Velocity

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Batch 1 (46+43 oC, with air reversal) Batch 2 (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

Air reversal time, minute 15

Superf vel (Ave ±StDev), m/min 11.20 ± 0.30 10.85 ± 0.37

Initial Paddy Layer (Ave±StDev), mm 517.8 15.6 507.8 7.5

Crack, Sun drying on Cement yard, 7-cm layer, %

Head Rice Recovery, %

Head Rice %, BEFORE drying 62.72 Differ 59.12 Differ

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BATCH 1 ( 43 o C, With air reversal ) BATCH 4 ( 43 oC, Without air reversal)

BATCH 5 ( 43 o C, With air reversal ) BATCH 8 ( 43 oC, Without air reversal)

Mẻ 1, Đảo gió, 43 oC

0 5 10 15 20 25 30

MẺ 4 (sấy 43 oC, KHÔNG đảo gió)

0 5 10 15 20 25 30

MẺ 5 (sấy 43 oC, CÓ đảo gió)

0 5 10 15 20 25 30

Mẻ 8 (sấy 43 oC, KHÔNG đảo gió)

0 5 10 15 20 25 30

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BATCH 3 (48 o C + 43 o C, With air reversal ) BATCH 2 (48 o C + 43 o C, Without air reversal )

BATCH 6 (49 o C + 43 o C, With air reversal ) BATCH 7 (48 o C + 43 o C, Without air reversal )

103

MẺ 2 (sấy 50oC + 43oC, KHÔNG đảo gió)

0 5 10 15 20 25 30

MẺ 7 (sấy 50 oC +43 oC, KHÔNG đảo gió)

0 5 10 15 20 25 30

MẺ 3 (sấy 50 oC + 43oC, CÓ đảo gió)

0 5 10 15 20 25 30

Mẻ 6 (sấy 50 oC +43 oC, CÓ đảo gió)

0 5 10 15 20 25 30

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.The SRA-1 dryer fan was tested for the performance (Fig.6)

SRA-1 FAN

0 5 10 15 20 25 30 35 40

M ech Eff, %

Power kW

Figure 6: Fan performance of the SRA-1 dryer

Originally, three factors were planned for study:

− Air reversal at 2 levels: a) YES , and b) NO

− Drying temperature at 2 levels: a) Constant at 43 oC ; and b) At 50 oC for the first hour, and afterwards constant at 43 oC

− Final moisture content at 2 levels: a) 14.5 % ; and b) 17.0%

Thus there would be 8 treatments, arranged in blocks, so that the initial moisture contents in each block are similar

However, in actual conditions, it was impossible to arrange for the blocks with same moisture content since the paddy belongs to the owner or the rice miller Eight experiments would last

at least 4- 8 days, thus even if the same paddy field were booked for the test, the initial MC would be different With different input MC, the final MC at 2 levels would not make sense,

at different drying rates

So we decided to conduct paired experiments, based on the first variable, namely with or without

The experiment results are summarized in Table 3 Figures 7 and 8 show the moisture reduction curves

4.3 Results and discussion (1-to dryer)

air reversal Each pair was combined with a level of the second variable (drying temperature) Each pair draw from the same lot of paddy input, thus could be assumed as having the same initial MC

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Table 3: Summary of 8 drying batches

50+43oC Without Air Reversal

43oC Without Air Reversal

43oC with Air Reversal

43oC with Air Reversal

43oC Without Air Reversal

50+43

oC with Air Reversal

/06 11 /12 /06 12/12/06 11- 12 /12 /06 14/12/06 13- 14/12/06 15/12/06 16/12/06

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l

43 o C Without Air Reversal

43 o C with Air Reversa

l

43 o C with Air Reversal

43 o C Without Air Reversal

50+43

o

C with Air Reversal

50+43 o C Without Air Reversal

19 Air SUPERFICIAL Velocity,

0.42

21 Air flow rate (m3 /s / ton) > 1.39 1.32 > 0.99 > 1.43

Ratio Reduction: Actual/ MC Calc 2.0 2.5 2.0 3.3 1.9 2.0 1.8 1.6

29 Bulk Density DRIED , kg / m 3 695 621 692 692 573 608 590 666

tune-up

Lots of immature, green grains

Batch 3 & 3: from same input paddy

- Very wet paddy, forced aeration for 1.5 hr to obtain desired initial MC

- Lots of immature grains &

impurities -Batch 5, 6& 7: from same input paddy

Good grain, little impurities

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BATCH 3 ( 43 o C, Without air reversal)

Batch 3 ( 43 oC, Without Air Reversal )

10 12 14 16 18

B atch 4 (43 o C, with Air R evers a l )

10 12 14 16 18 20 22 24 26 28

0 1 2 3 4 5 6 7 8 9 10 11 12

Drying tim e, hr

T1 T2 T3 T4 T5 D1 D2 D3 D4 D5

Batch 6 (43 oC, Without Air Reversal )

Batch 6 (43 oC, Without Air Revers al )

10 12 14 16 18

Batch 5 (43 oC, with Air Reversal )

Batch 5 (43 oC, with Air Reversal )

10 12 14 16 18 20 22 24 26 28

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108

Batch 8 (50 oC + 43 oC, WITHOUT Air Reversal

Batch 8 (50 oC + 43 oC, WITHOUT Air Reversal

10 12 14 16 18 20 22 24 26 28

Batch 7 (50 oC + 43 oC, with Air Reversal )

Batch 7 (50 oC + 43 oC, with Air Reversal )

10 12 14 16 18 20 22 24 26 28

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The following remarks could be pointed out:

- The effect of air reversal was very apparent in reducing the final moisture differential (FMD) Without air reversal this FMD was larger than 2 % point With air reversal, it was less than 2 % point; even that the grain quantity dried was much more than the former case

- For this lab dryer, air reversal did not decrease the drying time, because for the same airflow, with less grain on the floor, the specific airflow rate (per ton) was higher in the case air was not reversed

- The drying temperature is stable and can be kept within ± 2 oC

The above remarks do not offer much new findings; yet the tests give specific and handy data for preparing training materials on rice drying, as part of the Project activities

The problem of non-uniformity of the input materials for testing is reflected with data on the bulk density of the input (wet) as well as the output (dried) paddy (Fig 9)

SRA-1, Ba-Ria VT, Dec.2006 (Wet paddy)

520 540 560 580 600 620 640

(a)

SRA-1, Ba-Ria VT, Dec.2006 (DRIED paddy)

500 550 600 650 700

Figure 9: Bulk density of the wet (a) and dried paddy (b) used in the tests

The learning experience from the tests have been: A balanced set of experimental data for

drying treatments of even 1 ton each is difficult to obtain under actual field conditions

Perhaps, a quantity of around 20 kg each is more appropriate Even so, cold storage room is needed for conditioning the grain for one-week-long testing Miscellaneous equipment such

as cleaner is also needed All these rigorous procedures would give pure academic results, which in fact do not reflect the realities, as the graph on the bulk density showed

Thus in the future, an alternative -that several drying researchers followed - would be modeling of the drying process This hopefully can cope with diversities in material conditions as well as ambient conditions

Another constraint was the laboratory milling equipment for milling analysis (for head rice

recovery) could not be standardized for proper operation at the time

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