Moisture Content Of Paddy Research Articles

Application of simulation in determining suitable operating parameters for industrial scale fluidized bed dryer during drying of high impurity moist paddy

A systematic approach has been developed for selecting the suitable drying parameters to be used for drying of high moisture and high impurity paddy with an industrial fluidized bed paddy dryer (10–20 t h−1 capacity) based on targeted specific air flow rate and residence time during two typical paddy drying seasons. A mathematical model was developed by modifying an existing model and was simulated and validated with observed industrial drying data as well as data reported in the literature. Comparison between the observed and simulated results showed that the mathematical model is capable of predicting outlet paddy moisture content and air temperature well. Suitable operating parameters were determined for reducing any initial paddy moisture content (mc) down to 24–25% dry basis (db), the safe mc level after fluidized bed drying to maintain rice quality, to achieve maximum possible throughput capacity of the dryer with corresponding energy consumption. Based on these criteria, bed thickness at 10 cm, specific air flow rate of 0.05 kg kg−1 s−1 (for corresponding bed air velocity of 2.3 m s−1), air temperature of 150 °C and residence time of 1.0 min were found to be suitable drying conditions for reducing paddy mc from 30 to 24.30% (db) in one season while the maximum throughput capacity of 15.7 tonne per hour (t h−1) might be achieved. The specific electrical and thermal energy were 0.48 and 6.15 MJ kg−1 water evaporated, respectively. On the other hand, the dryer capacity was found to be limited to 7.4 t h−1 during drying paddy of higher initial mc (35% db). This approach might provide easy and comprehensive guidelines for selecting suitable sets of operating parameters for any industrial fluidized bed dryer at its possible maximum throughput capacity for drying of freshly harvested high moist paddy with a high level of impurities.

Energy and Quality Attributes of Combined Hot-Air/Infrared Drying of Paddy

The kinetics of combined hot-air/infrared thin-layer drying of paddy was studied. The mechanical quality aspects of paddy kernels dried at different drying conditions were evaluated in terms of percentage of cracked kernels and also required failure force obtained from bending tests. The well-known Artificial Neural Network (ANN) modeling technique was applied to predict the drying time, variations in paddy moisture content, the percentages of cracked kernels, and the values of required failure force of paddy at different drying conditions. The best ANN topologies, transfer functions, and training algorithms were determined for prediction of the mentioned parameters. In addition to the product quality aspects, the specific energy consumption (SEC) was estimated for all drying conditions. The results indicated that application of a low-intensity IR radiation (2000 W/m2), together with lower values of inlet air temperature (30°C) and moderate values of inlet air velocity (0.15 m/s), can effectively improve the final quality of paddy (as a heat-sensitive product) with a reasonable SEC.

Popping characteristics of paddy using microwave energy and optimization of process parameters

Microwave popping characteristics of a particular variety of paddy were studied using a domestic microwave oven. The experiments were carried out at 4 levels of moisture content (around 13%, 14%, 15% and 16% wb), 3 levels of power (600 W, 850 W and 1000 W) and 5 levels of heating time (40 s, 60 s, 80 s, 100 s and 120 s). A general factorial experiment design was followed, and effect of different treatment combinations on popping percentage and expansion ratio of the paddy was evaluated. The maximum popping percentage of 63.47% was obtained at a moisture content of 14.15% and energy level of 80 kJ (1000 W and 80 s) while the maximum expansion ratio of 4.42 was obtained at 14.94% moisture content and energy level of 68 kJ (850 W and 80 s). Optimum values of microwave power, time of heating and moisture content of paddy were achieved at 1000 W, 80 s and 15%, respectively, corresponding to popping percentage and expansion ratio of 58.73 and 3.58.

Popping characteristics of paddy using microwave energy and optimization of process parameters

Microwave popping characteristics of a particular variety of paddy were studied using a domestic microwave oven. The experiments were carried out at 4 levels of moisture content (around 13%, 14%, 15% and 16% wb), 3 levels of power (600 W, 850 W and 1000 W) and 5 levels of heating time (40 s, 60 s, 80 s, 100 s and 120 s). A general factorial experiment design was followed, and effect of different treatment combinations on popping percentage and expansion ratio of the paddy was evaluated. The maximum popping percentage of 63.47% was obtained at a moisture content of 14.15% and energy level of 80 kJ (1000 W and 80 s) while the maximum expansion ratio of 4.42 was obtained at 14.94% moisture content and energy level of 68 kJ (850 W and 80 s). Optimum values of microwave power, time of heating and moisture content of paddy were achieved at 1000 W, 80 s and 15%, respectively, corresponding to popping percentage and expansion ratio of 58.73 and 3.58.

GPR System for Monitoring Paddy Moisture Content in a Drying Process

High-frequency ground penetrating radar (GPR) was used in this study to monitor the moisture content of paddy in a drying process. The reflected radar pulses were used to calculate the dielectric constant of paddy. Owing to the temperature increase, Nelson and Noh's quadratic model was extended by introducing a temperature correction factor adapted to predict the dielectric constants at different temperatures. The calculated paddy moisture content was in good agreement with the values measured by the conventional oven method. Our results demonstrate the potential use of GPR systems as an online tool for monitoring the paddy moisture content in the drying process.

Energy and rice quality aspects during drying of freshly harvested paddy with industrial inclined bed dryer

The performance evaluation of any industrial dryer regarding energy consumption and product quality should be assessed to check its present status and to suggest for further efficient operation. An investigation was carried out to evaluate the impact of drying temperature and air flow on energy consumption and quality of rice during paddy drying with industrial inclined bed dryer (IBD) with average holding capacity of 15 ton in the selected complexes of Padiberas Nasional Berhad (BERNAS)-the national paddy custodian of Malaysia. In reducing paddy moisture content (mc) from 22% to 23% wet basis (wb) down to around 12.5% wb, the final mc, the specific electrical (in terms of primary energy) and the specific thermal energy consumption were found to be varied between 1.44 to 1.95MJ/kg water evaporated and 2.77 to 3.47MJ/kg water evaporated, respectively. Analysis revealed that the specific electrical energy consumption was around 20% lesser and the specific thermal energy consumption of IBDs was around 10% higher during drying with air temperature of 41–42°C than drying with 38–39°C in reducing paddy mc from 22% to 23% (wb) down to around 12.5% (wb). However, paddy being with almost same initial mc dried using drying temperature of 38–39°C, IBDs yielded 1–4% higher head rice yield while milling recovery and whiteness were comparable at acceptable milling degree and transparency. The bed air flows between 0.27 and 0.29m3m−2s−1 resulted in higher head rice yield slightly while its effect on drying time was not prominent so much. For paddy with initial moisture content below 23% wb, it is recommended that drying air temperature should not be higher than 39°C in order to maintain rice quality at reasonable energy consumption.

An investigation of the effects of harvesting time and milling moisture content of paddy on the quality of milled rice

Paddy harvest time (PHT) and its moisture content at milling process (MCMP) are two major factors determining the milling quality of rice. In this regards, a field research was conducted to study the effect of these factors on milled rice breakage (MRB) and ratio of cracked kernels (RCK) of Hashemi paddy cultivar in north of Iran. Five harvest times of 24, 27, 30, 33, 36 days after fifty percent flowering (DAFPF) and four milling moisture contents of 8-9, 10-11, 12-13, and 14-15% dry basis (d.b.) were considered for the research. Results showed that the effects of PHT and MCMP were significant on the MRB and RCK (P < 0.01). The lowest (16.32%) MRB was recorded at 30 DAFPF; however there was no significant difference between values at 27 and 30 DAFPF (17.02 and 16.32%, respectively). Results also indicated that the lowest (9.84%) MRB mean was obtained at 8-9% d.b. of MCMP. The least (1.813%) RCK was obtained at 27 DAFPF; however there was no significant difference between the RCK at 27 and 30 DAFPF (1.813 and 1.750%, respectively). Besides, the lowest mean values of RCK (1.048 and 1.288%) were determined at 8-9 and 10-11% MCMP. As a final conclusion, in order to gain the least MRB and RCK, the most suitable situations for harvesting and milling the ‘Hashemi’ cultivar in north of Iran were determined to be harvesting at 30 DAFPF and milling at PMC of 8-9% d.b.

Drying of High-Moisture Paddy Using a Combined Impinging Stream and Pneumatic Drying System

A system combining the principles of impinging stream drying and pneumatic drying (ISD-PD) for high-moisture paddy was developed to increase the energy efficiency of the drying process. The effects of inlet air temperature and paddy feed flow rate on the overall performance, in terms of the volumetric water evaporation rate and volumetric heat transfer coefficient, and energy consumption of the system were then investigated. The dried paddy quality in terms of the head rice yield and whiteness was also assessed. The results were compared with those obtained from a system consisting only of a pneumatic dryer. It was found that an increase in the inlet air temperature and paddy feed flow rate led to an increase in the volumetric water evaporation rate. The volumetric heat transfer coefficient varied insignificantly with the inlet air temperature but increased with the paddy feed flow rate. The moisture content of paddy was reduced from its original value by 6.6 to 9.7% (db) within a very short period of time. The mean residence time of the paddy was increased by 33 to 41% via the use of the ISD-PD system, leading to moisture reduction rates 55–166% higher than those for the pneumatic dryer. The head rice yield decreased with an increase in the inlet air temperature and paddy feed flow rate. On the other hand, the effects of inlet air temperature and paddy feed flow rate on whiteness was not significant.

In Situ Moisture Content Monitoring Sensor Detecting Mutual Coupling Magnitude Between Parallel and Perpendicular Dipole Antennas

This paper presents an in situ moisture content sensor based on a switched-polarization dipole antenna that detects the magnitude of mutual coupling between perpendicular and parallel polarizations. Three aspects of the sensor development are presented: a new closed-form calculation of mutual impedance of perpendicular polarization dipole antenna, an antenna design, and an investigation of performance enhancement. As the sensor detects only the magnitude of mutual coupling, it is low cost and low profile and needs less processing time. Thus, it is suitable for a closed-loop drying system. Our study has shown that the values of the dielectric constants measured by this sensor are comparable to the reference values from the transmission line technique in the previous work. However, there are significant differences in the values of the dielectric loss factors because the structure of the presented sensor is not a closed boundary like the transmission line sensor. Therefore, error compensation has been developed to correct the results. This sensor, in a closed-loop drying system, has shown good performance for in situ monitoring and real-time monitoring. Consequently, it is very suitable for monitoring the moisture content of paddy (rough rice).

Flow Properties of Awned and De-Awned Paddy Grains Through a Horizontal Hopper Orifice

In a modern rice mill, de-awning is an important process before husking operation to eliminate awns of the paddy grains for easy conveying in the elevators, chutes, and hopper orifices. This experiment was conducted to study the effects of independent variables of de-awning percentage, orifice cross-sectional area and paddy grains moisture content on the flowing rate (FR) and variations of flowing rate (VFR) of paddy grains through a horizontal hopper orifice. A local paddy variety, namely, Hashemi, which is characterized by long awns was used as a raw material in the test. The results indicated that flow rate (FR) and variations on flow rate (VFR) significantly (p < 0.01) affected by the de-awning percentage, orifice cross-sectional area and paddy moisture content. FR increased from 45.00 to 87.57 g s−1 and VFR decreased from 54.93 to 21.49%, as de-awning increased from 14.67 to 84.93%. FR increased as the orifice cross-sectional area increased from 12.08 to 34.81 cm2; however, higher VFR was obtained at lower orifice cross-sectional area. For the awned (87% of the grains had originally awns) and de-awned paddy (82% of the grains were de-awned), FR decreased as the paddy moisture content increased from 8.67 to 15.06%wb; while VFR increased at higher grain moisture content.

Influence of Storage Period on Physical Properties and Quality of Paddy Stored in GIC Silo and Bag Storage under Humid Konkan Climatic Conditions

Experiment was conducted to study the influence of storage period and type of storage on the physical properties (bulk density, thousand grain weight, germination, insect infestation, protein content and ash content) and quality of paddy grain stored in galvanized iron corrugated silo and bag storage under humid Konkan climatic conditions. It was found that duration of storage had a profound effect on some of the properties and quality of stored paddy grain. Bulk density of paddy decreased from 510 to 502 kg.m-3 in silo storage and 510 to 501 kg.m-3 in bag storage, thousand grain weight of paddy decreased from 19.3 g to 18.4 g in silo storage and 19.1 g to 17.6 g in bag storage, germination percentage of paddy decreased from 70.6% to 52.3% in silo storage and 69.5% to 49.3% in bag storage, insect infestation increased from 4.7% to 18.8% in silo storage and 4.4% to 20.2% in bag storage, protein content of paddy grain decreased from 8.78% to 7.89% in silo storage and 8.33% to 7.40% in bag storage, ash content of paddy increased from 7.30% to 8.75% in silo storage and 8.20% to 9.20% in bag storage during storage period of 10 months. The moisture content of paddy increased between the month of May and July in both silo and bag storage, and did not vary significantly during the other periods.

Effects of Simultaneous Parboiling and Drying by Infrared Radiation Heating on Parboiled Rice Quality

An infrared (IR) radiation heating and vibrating apparatus was used to study a simultaneous parboiling and drying process. Physicochemical properties such as milling yield, color, and pasting properties of parboiled paddy were evaluated. Radiation intensity levels of 46.7 kW/m2, variable exposure time, and rice samples at fixed initial moisture contents (IMC) of 30 and 32% wet basis (wb) were used. It was discovered that the radiation intensity of 46.7 kW/m2 and 32% wb moisture content yielded a quality level similar to that of conventional steam-parboiled rice. The head rice yield (HRY) of IR paddy slightly decreased with increased exposure time. The HRY of IR heating was more than 60% compared to HRY values of 67.68 to 69.34% for conventional steam-parboiled rice. The b-values of 23 to 25 for IR samples showed lighter yellowness than the 29.7 b-value of conventional steam-parboiled rice. The pasting properties of all IR samples showed lower viscosity compared to the raw-milled rice samples but higher than conventional steam-parboiled rice. Initial moisture content of paddy affected the degree of starch gelatinization (SG) by differential scanning calorimetry (DSC). Under IR heating for 18 min of exposure time, the 32% wb IMC sample showed SG at 80.15% compared to SG at 59.02% with the 30% wb IMC sample. Hence, while employing simultaneous parboiling and drying with IR heating for an exposure time of 18 min, the sample retained more parboiled flavor as a result of a higher degree of starch gelatinization. The sample showed lower HRY, but yellowness was within the acceptable range. Energy requirement for producing 1 ton of parboiled paddy by the IR heating process is lower than the conventional steam-parboiled process but statistically nonsignificant (P > 0.05). However, the process time was reduced to one third of the conventional process, leading to improved quality. In addition, initial investment cost was minimal because a steam generator was not required.

EFFECT OF DE‐AWNING AND MOISTURE CONTENT ON SOME FRICTIONAL PROPERTIES OF PADDY

ABSTRACTOne of the specific traits of Iran's local paddy varieties is the presence of awns at the tip of the lemma that cause difficulties in the grain flow through chutes and orifices. In this study, the effect of de‐awning and moisture content of paddy on the angle of repose, coefficient of internal friction and coefficient of mobility were evaluated as a function of moisture content in the range of 7–23% dry basis (d.b.).Results revealed that the effect of de‐awning and moisture content on frictional properties of paddy was highly significant (P &lt; 0.01). For awned paddy, the angle of repose increased from 37.42 to 45.70°; coefficient of internal friction increased from 0.453 to 0.574; the angle of internal friction from 24.37 to 29.85° and coefficient of mobility decreased from 0.415 to 0.335 as the paddy moisture content increased from 7.64 to 23.38% d.b. In the case of de‐awned paddy, the angle of repose increased from 34.46 to 42.68°; coefficient of internal friction from 0.427 to 0.512; the angle of internal friction from 23.11 to 27.10° and the coefficient of mobility decreased from 0.430 to 0.370 at same range of moisture content.PRACTICAL APPLICATIONSKnowledge of frictional properties is important in predicting the lateral pressure on a retaining wall in storage bins or design of bins and hoppers for gravity flow. The coefficient and angle of internal friction has applications in problems of flow of bulk granular materials encountered in problems flow of bulk granular materials equipment. To predict the flow ability of the grains through openings, it is important to determine the angle of repose of the materials. In design and optimization of paddy handling systems, especially de‐awner machine, dryer, huller and cleaning systems, it is important to obtain these frictional properties during paddy postharvest operations.

Effect of Rollers Differential Speed and Paddy Moisture Content on Performance of Rubber Roll Husker

This study was carried out at the Rice Research Institute of Iran (RRII) to investigate the effect of rollers differential peripheral speed of commercial rubber roll husker and paddy moisture content on the husking index and percentage of broken rice. The experiment was conducted at six levels of rollers differential speed (1.5, 2.2, 2.9, 3.6, 4.3 and 5 m s -1 ) and three levels of paddy moisture content (8-9, 10-11 and 12-13% w.b.). Two common paddy varieties, namely Binam and Khazer, were selected for this study. Results revealed that the effect of rollers differential speed and moisture content significantly (P<0.01) affected percentage of broken brown rice and paddy husking index. Average broken kernel percentage increased from 13 to 14.61% while husking index decreased from 71.64 to 61.81%, as paddy moisture content increased from 8-9 to 12-13%. It was observed that amount of broken rice decreased from 18.83 to 9.97%, when rollers differential speed varied from 1.5 to 5 m s -1 , while the husking index initially increased and then started to decrease. The mean value of husking index for Khazar variety (64.71%) was significantly lower than that for Binam variety (69.2%). It was concluded that rollers differential speed of 2.9 m s -1 and moisture content of 8-9% was the most appropriate combination for paddy husking of Binam and Khazar varieties in rubber roll husker. Keyword: Paddy husker, Hulling index, Broken rice, Rollers speed.

Study on In-store drying technology of paddy in China

In China, with accelerating growth of agriculture economy structure and rapid development of farming mechanization, the intensity and scale of grain planting has increased considerably. However, the drying of freshly harvested grain is a big problem needing to be resolved. In-store drying technology has good ability for large scale drying. Low energy consumption and successful application of this technology in Australia and America has attracted much attention by the Chinese government. Therefore, study of instore drying started in China from the cooperative study of ‘In-store drying of paddy in China’ with Australia in 1997. This paper will introduce the main projects of in-store drying in China since 1997, different periods of the technology development, key problems solved, major achievements and the drying technology distribution within China. After about 13 years development, in-store drying of paddy in China includes technology and related equipment specifically for China, such as technology and equipment for mobile ventilation, mold prevention with ozone, heaters for drying grain moisture, and computerized cooling systems. The initial moisture content of paddy allowed for in-store drying increased from 16% to 25%, the bulk allowable depth of paddy increased from 1.8 m to 6 m, and was competitive with paddy drying throughout the world. The main tasks to advance in-store drying in China in the future will be integration of two stage drying technology for paddy and development of relevant equipment, wireless control ventilation technology and development of relevant equipment, study and application of in-store drying technology in new varieties such as wheat and rapeseed. Keywords : China, In-store drying, Paddy, Moisture content

Sequential modeling of fluidized bed paddy dryer

A sequential method was developed to model a continuous plug flow fluidized bed dryer. The method is based on dividing the dryer into sections in series with ideal mixing for both solid and gas phases in each section. In order to determine the proper number of sections, drying experiments were carried out using paddy at different operating conditions. It was shown that the number of sections can be correlated to Damköhler number, which includes kinetic and hydrodynamic parameters of the process. The model is able to predict the particle’s moisture profile along the bed as well as the moisture content of dried product. It was shown that the model fits the experimental data satisfactorily with the correlation coefficient of 0.989. Moreover, the model was tested against available data in the literature at different scales and operating conditions for which an error of less than 4.5% was observed in predicting the paddy moisture content at the outlet.

고주파 저항방식 함수율계의 보정식 개발 및 특성평가

This study compared moisture content measured by moisture meter of microwave resistance type(MMMRT) and standard moisture content of paddy, and developed the correction equation using linear and curvilinear regression analysis, and to explore its significance test. The correction factor according to the range of moisture content was developed to improve the measurement precision of MMMRT. The results were as followings. The coefficients of determination of correction equation by linear and curvilinear regression analysis with comparing the MMMRT and standard moisture content were 0.946 and 0.968, respectively. The moisture content error of MMMRT and standard moisture content measured after the MMMRT were corrected by moisture content rate of every 5% using the correction equation by curvilinear regression analysis appeared with 0~0.5% and 0.9~1.8% respectively in the moisture content range of 15~20% and 20~25%.

Evaluation of performance and energy consumption of an impinging stream dryer for paddy

Impinging stream dryer has proven to be an excellent alternative means for removing surface moisture of particulate materials. In this study, a coaxial two-impinging stream dryer prototype for paddy, whose surface moisture needs to be removed prior to subsequent processing, was developed and tested. The effects of various operating and geometric parameters, i.e., inlet air temperature, impinging distance, particle flow rate and particle feeding characteristics (single-point feeding vs. double-point feeding), on the overall performance (in terms of the volumetric water evaporation rate and volumetric heat transfer coefficient) and energy consumption of the dryer were then studied. It was found that the developed impinging stream dryer could reduce the moisture content of paddy by 3.4–7.7% (d.b.) within a very short period of time. The maximum value of the volumetric water evaporation rate was found to be about 198 kg water /m 3 h, while the maximum value of the volumetric heat transfer coefficient was about 7013 W/m 3 K. The mean residence time of the particles (paddy) in the system was in the range of 1.81–2.42 s, leading to average drying rate in the range of 1.52–3.83 (% d.b.) s −1 , which is about 250 and 40 times higher than spouted-bed and fluidized-bed dryers, respectively. The lowest total specific energy consumption of the process was 5.1 MJ/kg water when using double-point particle feeding at an inlet air temperature of 110 °C, an impinging distance of 5 cm and particle flow rate of 150 kg dry solid /h.

Relationship of starch changes to puffing expansion of parboiled rice

'Intan' variety of paddy (Oryza sativa) was tested for puffing. It was parboiled under a wide range of paddy moisture content, steaming pressure and time, as also temperature and time of sand heating. The resulting milled rices were studied for their diverse properties including puffing. Indices of starch changes in the samples were calculated as: (1) gelatinisation index from the solubility of amylose in 0.2 N KOH; (2) amylopectin retrogradation from the post-production drop in room-temperature hydration power of the parboiled paddy during air-drying, (3) thermal breakdown of starch from the drop in gel permeation chromatographic fraction I of starch; lipid-amylose complexation indirectly from (4) drop in rate of water uptake during cooking and (5) cooked-rice firmness. It was found that the puffing expansion was very highly correlated with the combined above 5 indices of starch changes, as much as 90% of the variation in puffing being explainable on that basis. Puffing was promoted by gelatinisation as well as lipid-amylose complexation, but was retarded by amylopectin retrogradation and probably starch breakdown.

DRYING CHARACTERISTICS AND MILLING QUALITY ASPECTS OF PADDY DRIED WITH GAS‐FIRED INFRARED

ABSTRACT Wet paddy was dried under different process conditions applying a laboratory gas‐fired infrared (GIR) dryer. Peak wavelength of infrared emitted and initial moisture content of paddy were varied to study the drying behavior. The available thin‐layer drying models were fitted to the drying data. Then, the modified Page model was chosen with higher coefficient of determination (R2 = 0.9985 − 0.9695) and best‐fitted over other models, based on comparing the values of root mean square deviation (RMSD), average percentage of error (%E) and chi‐square (χ2) between the observed and predicted moisture ratios. Qualities of GIR and temper‐dried wet paddy in terms of head rice yield and whiteness were evaluated. Response surface methodology found that an increase in GIR drying time could increase head rice yield. However, an increase in both GIR drying time and tempering time could decrease the whiteness. The contour overlay graph could then be used for determining the appropriate drying conditions, depending on the industrial or user requirement.PRACTICAL APPLICATIONSInfrared (IR) drying technology has appeared as one of the potential alternatives to the traditional heating methods for obtaining high‐quality dried agro‐products. For long‐grain paddy drying, there is at present a dearth of reports exploring IR drying kinetics, and even in such reports, milling quality was the focus of investigation with respect to appropriate drying process conditions. This study has presented the modeling determination and explanation on milling qualities of paddy dried with gas‐fired infrared dryer. The drying process has provided a guideline on basic information to build a commercial drying system. Finally, these results would have practical applications for maintaining or increasing the milling qualities of paddy in the existing industry.