MANAGING MOIST PADDY BY DRYING, TEMPERING AND AMBIENT AIR VENTILATION

This paper describes a strategy for reducing moisture in paddy by fluidized bed drying, tempering and ambient air cooling. Experimental results showed that after the three processes, moisture content was reduced from 33 % to 16.5 % dry-basis within approximately 53 minutes. During the first process, a fluidized-bed dryer was used to reduce the moisture content of paddy down to 19.5 % dry-basis within 3 minutes. Then the paddy was tempered for 30 minutes. Finally, it was cooled by ambient air (temperature and relative humidity of 30 °C and 55-60% respectively) with air velocity of 0.15 m/s for 20 minutes. Quality of paddy in terms of head rice yield and whiteness was acceptable.     

MANAGING MOIST PADDY BY DRYING,TEMPERING AND AMBIENT AIR VENTILATION

ABSTRACT

This paper describes a strategy for reducing moisture in paddy by fluidized bed drying, tempering and ambient air cooling. Experimental results showed that after the three processes, moisture content was reduced from 33 % to 16.5 % dry-basis within approximately 53 minutes. During the first process, a fluidized-bed dryer was used to reduce the moisture content of paddy down to 19.5 % dry-basis within 3 minutes. Then the paddy was tempered for 30 minutes. Finally, it was cooled by ambient air (temperature and relative humidity of 30 °C and 55-60% respectively) with air velocity of 0.15 m/s for 20 minutes. Quality of paddy in terms of head rice yield and whiteness was acceptable.     

EFFECTS OF DRYING, TEMPERING AND AMBIENT AIR VENTILATION ON QUALITY AND MOISTURE REDUCTION OF CORN

The objective of this work is to study systematically how to decrease corn moisture content using processes consisting of fluidized bed drying, tempering and ambient air ventilation. Effects of drying, tempering and ventilation on moisture reduction and quality of dried corn in terms of stress crack, breakage and color are experimentally investigated. Experimental results show that stress crack depends on final moisture content of com. Tempering is found useful for increasing the quality of dried com after fluidized bed drying. The optimum tempering time is 40 minutes. Among the ambient air velocity ranging from 0.075 to 0.375 m/s, the appropriate velocity is 0.15 m/s. Final moisture content of com after ambient air ventilation is about 13.0 - 14.5 %(w.b.) with breakage and stress crack lower than 2% and 5% by wt., respectively. Slight change of color of dried corn is observed.     

CORN QUALITY AFTER DELYING BY FLUIDIZATION TECHNIQUE AT HIGH TEMPERATURE

ABSTRACT

Corn quality, in terms of stress crack, breakage and colour, after drying by fluidization technique was investigated. Drying air temperatures for this study were 150, 170 and 200°C. Experimental results showed that drying corn of 43% (d.b.) initial moisture content to 16% (d.b.) final moisture content (approximate 9 minutes) with drying air temperature up to 170°C (inlet air relative humidity less than 5%) could be done without significant loss of quality, i.e. no breakage of corn kernel, stress crack less than 12% and just small change of colour of grain surface. Empirical equations describing evolution of multiple stress crack and grain surface colour were developed. Results obtained from the equations are in good agreement with experimental ones.     

CORN QUALITY AFTER DELYING BY FLUIDIZATION TECHNIQUE AT HIGH TEMPERATURE

Corn quality, in terms of stress crack, breakage and colour, after drying by fluidization technique was investigated. Drying air temperatures for this study were 150, 170 and 200°C. Experimental results showed that drying corn of 43% (d.b.) initial moisture content to 16% (d.b.) final moisture content (approximate 9 minutes) with drying air temperature up to 170°C (inlet air relative humidity less than 5%) could be done without significant loss of quality, i.e. no breakage of corn kernel, stress crack less than 12% and just small change of colour of grain surface. Empirical equations describing evolution of multiple stress crack and grain surface colour were developed. Results obtained from the equations are in good agreement with experimental ones.     

Drying kinetics and effective moisture diffusivity of purslane undergoing microwave heat treatment

The effects of microwave drying on moisture content, moisture ratio, drying time and effective moisture diffusivity of purslane leaves (Portulaca oleracea L.) were investigated. By increasing the microwave output power (180–900W) and the sample amounts (25–100 g), the drying time decreased from 43 to 12.5 minutes and increased from 27 to 54 minutes, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among the models proposed, the semi-empirical Midilli et al. model gave a better fit for all drying conditions applied. By increasing the microwave output power and decreasing the sample amount, the effective moisture diffusivity values ranged from 5.913×10⁻¹¹ to 1.872×10⁻¹⁰ m²/s and from 9.889×10⁻¹¹ to 3.292×10⁻¹¹ m²/s, respectively. The activation energy was calculated using an exponential expression based on the Arrhenius equation.     

STUDIES ON STIFLING AND DRYING OF COCOONS FOR LONGER STORAGE

ABSTRACT

Long term storage of stifled cocoons is an important problem during unfavourable seasonal conditions. Cocoons could be stifled within 20 minutes by using steam al 90°C. The shade drying of steam stifled cocoons in thin layers reduced the moisture content from 228 per cent (db) to 3 1.7 per cent (db) within 10 days. By hot air conditioning method the cocoons could be stifled and dried simultaneously. Using hot air at 90°C the cocoons could be stifled within 10 minutes, and dried to the equilibrium moisture content within 2 hours. The cocoons stifled by the hot air conditioning method could be reeled even just after stifling.     

叠氏污泥脱水技术处理炼油厂“三泥”

分析了炼油厂“三泥”性质和脱水预处理对策,介绍了叠氏污泥脱水机特点原理及处理炼油企业“三泥”的典型应用实例.当处理罐底泥时,进料含水率在86.7％～90.2％时,经叠氏污泥脱水机脱水后泥饼含水率降为54.2％～55.9％;当处理剩余活性污泥时,进料含水率在95.5％～97.5％时,经叠氏污泥脱水机脱水后泥饼含水率降为78.0％～79.0％;当处理浮渣时,进料含水率在90.5％～92.0％时,经叠氏污泥脱水机脱水后泥饼含水率降为67.9％～68.7％.所处理物料的脱水泥饼的含水率均低于80％,满足污泥迸一步处理前的脱水需求,与离心机相比节电在1/10以上.     

潮湿褐煤干法分选实验研究

为提高空气重介质流化床对入料煤水分的适应性,以热气代替常温空气改善流化床对褐煤的分选效果。采用可能偏差Ep为评价指标,研究了热态空气重介质流化床的干燥温度、干燥时间和风量对褐煤分选效果的影响。结果表明:干燥温度为30~50℃时,干燥温度越高,Ep越低;干燥时间为1~5 min时,干燥时间越长,Ep越低,超过3 min后,Ep降低缓慢;风量为8~12 m3/h时,风量增大,Ep先降低后升高。煤样表面水分越高,干燥温度、干燥时间和风量变化对Ep影响越显著。表面水分1%的褐煤,干燥温度50℃、干燥时间5 min、风量10 m3/h时,褐煤分选效果最好,Ep可达到0.022g/cm3。实验证明热态空气重介质流化床可用于分选潮湿褐煤。     

Drying powdered coal with the aid of ultrasound

The results of introducing ultrasound into three different drying processes has been discussed. The processes included: (1) static drying of a layer of powdered coal with airborne ultrasound, (2) rotary kiln drying with airborne ultrasound, and (3) drying of powdered coal on a sloping, ultrasonically vibrated metal trough. In all three processes, the introduction of ultrasound increased the drying rate.

The frequency of ultrasound used was 20 kHz with sound intensities up to 165 dB. The pulverized coal used had a size range from 400 μm to less than 2 smm, with 65% being less than 150 μm in size. Air temperatures used varied from 65 to 300 °C.

The most energy-efficient drying process with ultrasound was found to be the sloping, ultrasonically vibrated trough. However, this process was limited to the use of an initial coal powder feed containing less than 10% moisture. For moisture contents above 10%, a dual drying system could be used. For example, the rotary kiln drier could be used ahead of the trough drier.

Both the static airborne ultrasound drying process and the ultrasonically vibrated trough drying process work best with a relatively thin layer of powdered coal. However, the residence time for the powdered coal being dried is measured in seconds for the sloping trough process in contrast to minutes for the static drying process. The static drying of a layer of powdered coal is also a batch-drying process while the rotary kiln and sloping trough are continuous processes. The advantages of the static airborne ultrasonic drying process would be: (1) closer control of the drying process, and (2) smaller quantities of powder can be used.     

Moisture conditioning of wood using a continuous microwave dryer

Lower moisture content in wood, preferably 5–6%, is desirable for many chemical modification reactions. Economically, it is not feasible to dry timber to such low moisture content by conventional drying without drying degrades. Microwave heating was evaluated and found to be effective in reducing the moisture content of radiata pine from 13% to 6% in a microwave cycle of two minutes. The energy consumption is about 55 kWh/m³. Moisture distribution profiles demonstrate very uniform drying across the sample thickness. The findings suggest that microwave heating can potentially be applied to condition wood in a very short period of time.     

The effect of dielectric heating on storage quality of cottonseed

Summary It was found that the exposure of moist cottonseed to a radio frequency electric field for a period of from two to five minutes effectively reduced the formation of free fatty acids during subsequent storage of the seed. Two primary factors were involved in this action. First, moisture was rapidly removed from the seed and second, the enzymes responsible for free fatty acid formation were destroyed. Cottonseed containing 20% moisture accumulated free fatty acids only very slowly on storage at 38.5°C. after a brief dielectric heat treatment. The temperature inside the cottonseed was measured during the dielectric heat treatment. Temperature above 100°C. were attained in less than one minute.     

The charring rate and charring depth of bamboo scrimber exposed to a standard fire

To better understand the charring properties of bamboo scrimber, a standard fire test was conducted to examine the effect of moisture content, exposure time, and grain direction on the charring rate of bamboo scrimber. The bamboo scrimber specimens were exposed to fire on one side with furnace temperatures following the requirements of ISO 834. The experimental results indicated the charring depth decreased as moisture content increased from 6% to 18%. Due to the thermal insulation of the char layer of bamboo scrimber, the charring rate decreased non‐linearly as the fire exposure time increased from 10 to 40 minutes. The charring rate of bamboo scrimber parallel to grain was approximately 1.23 times that perpendicular to grain. The non‐linear equation to express the charring rate of bamboo scrimber with moisture content, exposure time, and grain direction was established by regression analysis of the test data. The temperature of the char front was approximately 280°C, determined by heat transfer analysis of the 3‐dimensional finite element method model. Compared with different timber species in the literature and in standards, bamboo scrimber has better fire performance and a lower charring rate.     

Microwave treatment of dehulled rapeseed to inactivate myrosinase and its effect on oil and meal quality

Rapeseed was dehulled using a Palyi pneumatic attrition system which produced 62–66% clean dehulled seed. Dehulled rapeseed was preconditioned to 7, 10 and 13% moisture levels, exposed to micro-wave irradiation for periods of up to 2.5 min and analyzed for residual thioglucoside glucohydrolase (myrosinase) activity. The 7% moisture samples heated slowly and required at least a 2.5 min treatment whereas 10 and 13% moisture samples heated more rapidly and required microwave exposures of 1.5 min or less for complete inactivation of the enzyme. The sulfur content of oils obtained from adequately microwave-treated samples (1.5 min for 10 and 13% and 2.5 min for 7% moisture samples) was equal to or lower than commercially processed crude rapeseed oils. The shorter microwave treatment of dehulled rapeseed produced considerably lighter oils and did not adversely affect the color of the meal. It also destroyed some of the rapeseed glucosinolates and improved the meal palatability. However, goitrogenic properties of microwave-treated rapeseed meal evaluated by mice feeding experiments did not appear different from untreated rapeseed meal.     

Selection of parameters for thermal treatment of soybeans by enzyme inactivation

The effects of thermal treatment, dry heat and steam on the physiologically active substances: urease and trypsin inhibitors of soybean products, were evaluated by means of urease activity and trypsin inhibitor activity. The parameters time and temperature, moisture and particle size were considered. From these analyses it can be concluded that the best conditions to obtain optimum soybean products were 25% of initial moisture content, exposed to steam (97 degrees C) during four to eight minutes.     

Moisture adsorption characteristics of a thin bed of polycrystalline potash pellets: Part II — Modeling and numerical simulation

This paper describes a numerical investigation of heat and moisture transfer in a bed of porous polycrystalline potash pellets. In this study a non-equilibrium mathematical model of temperature and moisture distribution within the bed was developed. Simulations were performed for a bed of potash pellets that is subjected to flows of humid air on the upper boundary and a cold impermeable surface on the lower boundary. The numerical predictions are in good agreement with the experiments and within the experimental uncertainty bounds. The model predicts that beds of porous potash pellets will contain less moisture than other types of potash fertilizer beds that are exposed to the same environmental conditions. The predictions also indicate that most of the accumulated moisture will be located in the top 10% of the bed and that the pore space relative humidity will be much greater than the supply air relative humidity.     

芦荟多糖的微波辅助提取及其保湿性能研究

通过微波提取技术从芦荟中提取芦荟多糖,采用单因素和正交试验,分别考察了微波辐射功率、时间、料液比、温度等因素对芦荟多糖提取率的影响。结果表明:微波时间为5 min,微波功率600 W,料液比1∶6 g/m L,温度为50℃时,提取工艺最佳,提取率为0.231 7%。通过干燥器控制湿度的方法对芦荟多糖提取物进行吸湿和保湿性能测试,结果表明芦荟多糖提取物是良好的保湿剂。     

Effect of moisture level on volatile carbonyls in cottonseed oil heated to 210C

Cottonseed oil containing 0, 2.5, 5 and 10% added moisture was heated to simulate food-frying conditions. The volatile carbonyls from the heated oil were crystallized as 2,4-dinitrophenylhydrazones and then regenerated for separation by gas-liquid chromatography. Nineteen peaks were observed for the dry oil; oil with added moisture had fewer peaks. Oil containing added moisture produced more total carbonyl by weight than did dry oil. Maximum production of carbonyls occurred in the oil with 2.5% added moisture. Approved as Journal Paper No. 448, College Experiment Station, University of Georgia, Athens.     

FLASH DRYING OF FISH MEALS WITH SUPERHEATED STEAM: ISOTHERMAL PROCESS

The work considers the application of the flash drying to the moisture removal of fishmeal using superheated steam as transport medium. Heat, momentum and mass transfer equations were applied and an algorithm based on these equations was developed and solved. The model was validated using experimental data obtained in a pilot pneumatic dryer ( total length 60 m) provided with a steam jacket to maintain the superheated steam at a constant temperature. The drying time was less than 10 s to decrease the fish meals moisture content from 53.5% to 28% d.b. and in a second pass by the dryer the moisture down to 16.9% using superheated steam at It 1 ° C and 130 ° C in the jacket. The computational results are in agreement with the experimental data.     

Microwave inactivation of thioglucosidase in intact crambe seeds

Optimum conditions for microwave inactivation of thioglucosidase in whole crambe seeds(Crambe abyssinica Hochst.) were investigated. Whole crambe seeds were left at 7% moisture or tempered to between 10 and 20% moisture contents prior to exposure to various microwave power inputs for 38 sec under controlled conditions. Ten percent moisture crambe seeds coupled the maximum percentage of microwave power. The amount of microwave energy required to inactivate thioglucosidase decreased as the moisture content of the seeds increased from 10 to 20%. Thioglucosidase could not be inactivated in 7% moisture seeds without burning the seeds. With 10, 15, and 20% moisture levels crambe seeds required a minimum of 0.70, 0.60, and 0.65 kW, respectively, of initial microwave power input and 18,12, and 11 kJ, respectively, of coupled energy to inactivate thioglucosidase. Optimum crambe seed moisture contents for microwave inactivation of thioglucosidase were determined to be between 14-16%.