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 COS

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

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 Van Tuan,

March 2007

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

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

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

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:

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:

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)

Figure 5: The 1-to dryer: Airflow upward; (b) Downward reverse airflow

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

25-26/7 25-7 30-7 24-7 27-7 23-7 29-7

Batch Number 1 5 4 8 3 6 2 7 Ave

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 - -

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

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

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

Average , m /minute 10.13 9.72 10.23 9.62 10.23 9.78 9.78 9.71 9.90

± Std Dev., m /minute 0.28 0.22 0.16 0.17 0.16 0.22 0.15 0.20

AIR FLOW, m3/s 5.31 5.10 5.37 5.05 5.37 5.13 5.13 5.10 5.19

Av Drying temp, oC 42.8 42.5 43.3 41.4 42.2 44.8 42.2 44.3 42.9

± Std.Dev, oC 2.0 2.8 2.4 2.8 3.6 2.8 3.6 3.2 2.9

Temp Increase, oC 16.2 16.25 12.41 12.14 12.0 11.83 12.0 12.20 13.1

Bulk density:Before, kg/m3 521 505 529 495 529 525 522 523 519

After drying, kg/m 3 480 484 465 493 498 515 477 503 489

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

Husk consumption: Total, kg 416.4 206.4 220.9 282.2 371.5 138.9 160.5 373.0

kg/ hour 39.95 34.40 21.04 36.41 37.16 38.80 27.92 31.96 33.45

Diesel consump :Total, Lit 18.0 17.0 16.6 12.0 17.00 6.0 9.50 17.0

Lit/ hour 1.73 2.83 1.58 1.55 1.70 1.68 1.65 1.46 1.77

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 No Drying temperature (oC) ± StDev 43.3 ± 3.1 43.0 ± 2.9

Drying time, h+xx/100 6.00 6.00

Initial MC, % (Ave ± StDev) 23.86 ± 0.71 20.41 ± 0.45

Final MC % (Ave ± StDev) 14.94 16.07

MC differential Top-Bottom, % 0.83 4.64

MC differential Middle-Top , % 2.24

AIRFLOW (20 points)

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

Rice husk consumption: kg / hr 28.5 35.9

Initial Paddy mass, kg 9276 9197

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

Crack BEFORE drying, % 12.00 Differ 21.00 Differ

Crack, Sun drying on Cement yard,

7-cm layer, %

Head Rice Recovery, %