luận văn nông nghiệp : 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 "


SECTION 3

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
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

4

5

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

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

9

Value losses due to field drying and sun drying ..........................................117

REFERENCES ........................................................................................................118

10 APPENDIX ..............................................................................................................119
10.1

Appendix 1 : 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)

1

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 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.

2

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


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

•

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.

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 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:
3.3.1

July 2006 experiments

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.
3.3.2

March 2007 experiments

Results are in Table 2. All 3 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- 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.

4

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 1 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 8 drying batches (July 2006 )
2523-7
25-7
Date /2006
26/7

30-7

24-7

27-7

23-7

29-7

Batch Number

1

5

4

8

3

6

2

7

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
3

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 2 drying batches

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
Batch Number

Batch 1
Batch 2
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

2

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