Modelling dehydration and quality degradation of maize during fluidized-bed drying

At harvest time, maize (Zea mays L.) has a moisture content too high to be stored, and has to be dried. To control the drying impact on maize characteristics, it is necessary to accurately know the spatial distribution of temperature and moisture content in the kernel, and the kinetics of quality loss in relation to these two factors. To this end, a physical model of heat and mass transfer in a maize kernel was designed. The Fick and Fourier equations were solved by the finite element method (FEM). The real 3D geometry of maize was obtained by NMR imaging and then used to build the mesh needed for the FEM computations. The model correctly describes the evolutions of maize moisture and salt-soluble protein content during fluidized-bed drying with a constant drying air temperature between 50 °C and 100 °C.     

Heating process of soybean using hot-air and superheated-steam fluidized-bed dryers

The present work investigated drying characteristics and inactivation of urease in soybean dried by superheated-steam and hot-air fluidized beds. The value of effective diffusion coefficient, which was determined by a method of slopes, was increased with increased drying temperature and increased moisture content. Furthermore, it depended on the type of heating medium, with higher moisture diffusion for soybean dried by hot air. Inactivation of the urease enzyme in both media showed difference in rate, in which the enzymatic inactivation was faster for soybean dried in superheated steam than in hot air. For the individual heating medium, the modified first-order reaction was adequately fitted to experimental data. The rate of inactivation was found to increase as the temperature and moisture content were increased. The urease enzyme was inactivated, along with maintaining protein solubility and lysine content being in standard range, as soybean was treated at a temperature between 135 and 150 °C for the hot air and the treatment temperature could be reduced to be lower than 135 °C by using superheated steam.     

Numerical model for biological fluidized-bed reactor treatment of perchlorate contaminated groundwater

Biological fluidized-bed reactor (BFBR) treatment with 1.3 mm granular activated carbon as support medium is being used for removal of 2.6 mg/L perchlorate from contaminated groundwater in California. The California drinking-water action level of 4 microg/L for perchlorate requires 99.9% perchlorate removal. Sufficient ethanol, the electron donor, is added to remove oxygen and nitrate as well as perchlorate, as all three serve as electron acceptors, but with biological preference for oxygen and nitrate. A numerical BFBR model based upon basic physical, chemical, and biological processes including reaction stoichiometry, biofilm kinetics, and sequential electron acceptor usage was developed and evaluated with the full-scale treatment results. A key fitting parameter was bacterial detachment rate, which impacts reaction stoichiometry. For best model fit this was found to vary between 0.062 and 0.31 d(-1), with an average of 0.22 d(-1). The model indicates that GAC particle size, reactor diameter, and perchlorate concentration affect BFBR performance. While empty-bed detention time might be decreased somewhat below 10 min by an increase in either GAC particle size or reactor diameter, the current design provides a good factor of safety in operation. With a 10 min detention time, the effluent goal of 4 microg/L should be achievable even with influent perchlorate concentration as high as 10 mg/L.     

An evaluation of fluidized-bed heating as a means of disinfesting wheat

Wheat of 14% m.c. containing all immature stages of Sitophilus oryzae (L.), Rhyzopertha dominica (F.) and Sitotroga cerealella (Oliv.) was exposed to air temperatures of 60, 70 or 80°C in a 10 kg capacity fluidized-bed operated with an airflow of 14.51 ls^?1 kg^?1 at 1.6 m s^?1. Exposures of 12, 6 and 4 min respectively produced grain surface temperatures of 59, 62 and 65°C and gave almost complete disinfestation. The required minimum exposure was determined by the heat tolerance of R. dominica which exceeded that of the other species. The moisture content of treated wheat was not changed appreciably and its baking quality was not impaired. Experiments with S. oryzae and R. dominica showed that the adults were also controlled by such exposures. The cost of fluidized-bed heating is discussed and appears to be comparable to that of recirculatory fumigation with methyl bromide.     

白腐菌Trametes hirsuta BYBF在三相流化床生物反应器产漆酶的研究

应用三相流化床生物反应器对Trametes hirsuta BYBF进行了产漆酶的研究,结果表明,菌丝球在流化床内稳定,能达到较好的流化状态,其最佳的条件为接种量10%,通气量0.3L/min,发酵5d后酶活即可达到3.36U/mL。并对白腐菌进行了重复分批培养,与摇床发酵相比,不仅提高了漆酶活力,而且也大大缩短了产酶周期,提高了生产效率。     

Reducing cracking and breakage of soybean grains under combined near-infrared radiation and fluidized-bed drying

Near-infrared radiation was combined with fluidized-bed drying to reduce the cracking and breakage of soybean grains because of its advantages such as a decrease in the moisture gradient and the stresses development within the grain kernel, leading to high quality of product. Physical qualities, i.e. cracking, breakage and colour, were investigated together with microstructure of soybean grains. Protein solubility and urease activity were also determined. The parameters studied were near-infrared radiation powers of 4, 6 and 8 kW, air velocity of 4.5 m/s, air temperature of 40 °C and grain bed depth of 6 cm. Results showed that the drying rate was increased with the increase of near-infrared radiation power. The moisture content was reduced from an initial moisture content of 20% d.b. to the final moisture contents of 13.5% d.b. (4 kW), 12.8% d.b. (6 kW) and 12.5% d.b. (8 kW). The cracking and breakage of soybean grains occurred negligible, which was lower than 4.4% and 5.3% for cracking and breakage, respectively. At near-infrared radiation powers of 4 and 6 kW was accepted for both soybean grains trade and animal feed industries in Thailand. The total colour difference changes (ΔE) were varied in the range of to 2.9-4.2. The protein solubility of final product was in an acceptable range (77-82%) for feed meal. The reduction of residual urease was varied in the range of to 39-70%. This study has demonstrated that the soybean grains under combined near-infrared radiation and fluidized-bed drying was properly treated.     

Heterogenous and homogenous catalytic oxidation by supported gamma-FeOOH in a fluidized-bed reactor: kinetic approach

Oxidation of benzoic acid (BA) by H2O2 was performed with a novel supported gamma-FeOOH catalyst in a circulating fluidized-bed reactor (CFBR). This study focused mainly on determining the proportions of homogeneous catalysis and heterogeneous catalysis in this CFBR. Also studied herein was how pH, H2O2 concentration, and BA concentration affect the oxidation of BA. Experimental results indicate that the decomposition rate of H2O2 was proportional to its concentration and that the oxidation rate of BA depended on both H2O2 and BA concentrations. The change in the rate constant of heterogeneous catalysis by pH was described in terms of ionization fractions of surface hydroxyl group. From the mathematical deduction, we can infer thatthe reaction rate associated with ...Fe(III)OH2+ is markedly higher than that with ...Fe(III)OH. Conclusively, although heterogeneous catalysis contributes primarily to the oxidation of BA at pH 4.4-7.0, the homogeneous catalysis is of increasing importance below pH 4.4 because of the reductive dissolution of gamma-FeOOH.     

Effect of high-temperature fluidized-bed drying on cooking, textural and digestive properties of waxy rice

In this work, changes of the cooking and pasting properties as well as starch digestibility of waxy rice (RD6) during hot air fluidized bed drying were investigated. Re-moistened waxy rice at an initial moisture content of 28% dry basis (d.b.) was dried at 90-150 °C. Semi-dried waxy rice was tempered and dried again by ambient air until the moisture content reached 16% (d.b). It was found that the degree of gelatinization increased with an increase in the drying temperature. At 130 and 150 °C the appearance of some waxy rice kernels changed from opaque to translucent, indicating complete gelatinization. Thermal degradation of amylopectin granules during high-temperature drying caused the starch to be more rapidly digested; this led to lower peak viscosity and setback viscosity. In addition, waxy rice processed at higher drying temperatures (90-150 °C) could adsorb more water and exhibited larger loss of solids during soaking. Such effects subsequently led to samples with lower hardness and higher stickiness. Based on the sensory analysis results, however, waxy rice dried at the above temperatures, when cooked, did not significantly differ in overall acceptability from the reference waxy rice.     

Freeze-drying in a fluidized-bed atmospheric dryer and in a vacuum dryer: Evaluation of external transfer coefficients

The factors which influence freeze-drying are classified as either internal or external. Internal factors derive from the properties of the material undergoing drying, while external factors relate to the physical conditions under which drying occurs. This paper looks at the external factors and compares them for two different freeze-drying methods: a vacuum dryer and an atmospheric fluidized-bed dryer containing an adsorbent.First, the ratio between the external heat and mass transfer coefficients, h/K, was evaluated: this ratio for the fluidized-bed dryer was constant at 398·8 kcal torr kg⁻¹ °C⁻¹ but varied for the vacuum dryer within the range 9·5 to 16·2 kcal torr kg⁻¹ °C⁻¹. The individual heat and mass transfer coefficients were calculated. The mass transfer coefficient, K, for the vacuum dryer was 1·0 kg h⁻¹ m⁻² torr⁻¹; for the atmospheric fluidized-bed dryer, K varied slightly with temperature, being 0·7, 0·8 and 1·0 kg h⁻¹ m⁻² torr⁻¹, at fluidized-bed temperatures of 0, −10 and −20°C, respectively. At these temperatures, the heat transfer coefficients for the fluidized-bed dryer were 287, 321 and 402 kcal h⁻¹ m⁻² °C⁻¹, respectively. For the vacuum dryer h was 9·5–16·2 kcal h⁻¹ m⁻² °C⁻¹. Thus, K values were comparable in the two drying systems but h in the fluidized-bed dryer was some 20–40 times greater than in the vacuum dryer.The study helped to elucidate the mechanisms involved during ice sublimation and contributed towards developing a means by which freeze-drying patterns could be predicted. The results were helpful in providing guidelines during the development of the novel atmospheric fluidized-bed technique.     

Electrostatic precipitator collection efficiency and trace element emissions from co-combustion of biomass and recovered fuel in fluidized-bed combustion

Particle and trace element emissions from energy production have continuously been subject to tightening regulations. At the same time, not enough is known on the effect of different combustion processes and different fuels and fuel mixtures on the particle characteristics and particle removal device operation. In this investigation, electrostatic precipitator fractional collection efficiency and trace metal emissions were determined experimentally at a 66 MW biomass-fueled bubbling fluidized-bed combustion plant. The measurements were carried out at the inlet and outlet of the two-field electrostatic precipitator (ESP) at the flue gas temperature of 130-150 degrees C. Two fuel mixtures were investigated: biomass fuel containing 70% wood residue and 30% peat and biomass with recovered fuel containing 70% wood residue, 18% peat, and 12% recovered fuel. The particle mass concentration at the ESP inlet was 510-1400 mg/Nm3. Particle emission at the ESP outlet was 2.3-6.4 mg/Nm3. Total ESP collection efficiency was 99.2-99.8%. Collection efficiency had a minimum in particle size range of 0.1-2 microm. In this size range, collection efficiency was 96-97%. The emission of the trace metals As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Tl, and V was well below the regulation values set by EU directive for waste incineration and co-incineration.     

基于嗅觉可视化技术的猪肉新鲜度检测

嗅觉可视化技术是使非可见物质成像（主要是气体成像）的一种无损检测新技术,属人工嗅觉模拟技术的一个新分支.使用卟啉和pH指示剂作为嗅觉可视化传感器阵列的气敏材料,检测猪肉中的优势致腐菌和新鲜度.将3种优势致腐菌-梭状芽孢杆菌、热死环丝菌、假单胞菌-分别接种至3组猪肉样本中,在3种温度--16℃,.4℃和20℃-条件下分别贮藏不同的时间后,采用扫描仪获取可视化传感器阵列与每个样本反应前后的图像信息;将阵列反应前后的颜色差值作为样本特征值,对不同的猪肉样本经不同贮藏时间后产生的挥发性气味,可视化传感器阵列显示其特定的颜色图像与其对应.结果表明,嗅觉可视化技术可以用于检测猪肉的优势致腐菌以及判断猪肉的新鲜度.     

畜禽饲养对动物源性产品质量安全的影响与防控对策

较详细地阐述了畜禽饲养环节对动物源性产品质量安全影响因素的来源,并根据分析的影响因素,针对性地提出了解决畜禽饲养环节动物源性产品质量安全的防控对策和思路.     

Prof. Dr. Dr. h. c. Dr. h. c. Bruno Huber

Ohne Zusammenfassung     

Prof. Dr.-Ing. Dr. h. c. Franz Kollmann Zum 65. Geburtstag

Ohne Zusammenfassung