碱式氯化镁纳米棒的干燥动力学方程

以六水氯化镁和轻质氧化镁为原料,采用液相法制备出碱式氯化镁纳米棒。在不同干燥介质温度和不同物料层厚度下,对碱式氯化镁纳米棒进行干燥动力学实验,得到其干燥曲线和干燥速率曲线。利用Origin软件对实验数据进行拟合,得到碱式氯化镁纳米棒的干燥方程为MR=exp[-(kt)n],干燥速率常数k=Aexp(-ERT)=Aexp[-EV(1+CLL)RT],n=1.808,A=6.3min-1,CL=37.4m-1,EV=14.1kJ/mol;以分段函数形式表示的干燥方程分别为:MR=exp[-(kt)n1](升速干燥阶段),n1=1.361;MR=a-mkt(恒速干燥阶段),a=1.074,m=0.633;MR=exp[-(kt)n2](降速干燥阶段),n2=2.109。     

基于薄层干燥模型的褐煤干燥动力学研究

在不同颗粒直径和不同的干燥介质温度下,对褐煤进行干燥动力学实验研究。得到了褐煤的干燥曲线和干燥速率曲线,采用薄层干燥模型对实验数据进行模拟,得到了褐煤的干燥方程和干燥速率方程。提出了褐煤干燥速率常数的经验公式k=A exp[（-E_v（1+C_dlnd））/（RT）],其中指前因子A=5.819min^-1,界面蒸发活化能E_v=21347.5KJ/mol,经验常数C_d=0.0409m^-1,干燥时间指数n=1.516。     

盐泥颗粒热风干燥特性及动力学模型

为优化盐泥颗粒干燥设备及结构参数，搭建热风干燥实验装置对盐泥颗粒进行热风干燥实验，研究不同风温、风速和堆积厚度对盐泥颗粒热风干燥特性的影响。对不同条件下的干燥特性曲线，通过比较决定系数R²、卡方x²和标准误差ESME等指标，评价5种常用干燥动力学模型对干燥曲线的拟合结果。结果表明：Midilli模型可以预测盐泥颗粒热风干燥过程水分的变化规律，模型预测的干燥曲线与实验干燥曲线有较高的拟合度。盐泥颗粒热风干燥过程中干燥速率逐渐下降，热风干燥特性与风温和堆积厚度密切相关。当温度从50℃增加到80℃时，有效水分扩散系数由2.038 39×10^-9 m²·s^-1增加到8.137 643×10^-9 m²·s^-1。     

藻渣热解特性及动力学分析

通过热重实验研究N₂气氛下升温速率对索氏提脂后的小球藻热解特性的影响,利用管式炉在N₂气氛下快速热解实验得出：在400℃时,小球藻热解转化率最高,生物油产率达57.6%,热解气为10%。采用等转化率方法FWO和KAS法对藻渣热解动力学进行分析和比较,结果表明：藻渣热解的主要热解阶段为25~800℃,可分为3个阶段,藻渣的DTG曲线存在两个失重峰,且随着升温速率提高,TG和DTG曲线都向高温区偏移,最大失重速率和残余固体质量都增加。N₂气氛条件下藻渣的主要热解阶段表观活化能和指前因子分别为228.46 kJ/mol和2.49×10²¹ min^-1,此阶段下FWO法和KAS法均能很好模拟藻渣热解数据,线性拟合相关系数（R²）均在0.96以上,最佳热解函数为dα/dT=2.49×10²¹/β exp（-228.46/（RT））（1-α）⁸。     

基于薄层干燥模型的碱式碳酸镁纳米花干燥动力学研究

在不同干燥介质温度和不同物料床层厚度下,对碱式碳酸镁纳米花进行干燥动力学实验,得到其干燥曲线和干燥速率曲线。采用薄层干燥模型对所得干燥动力学实验数据进行数学处理,得到碱式碳酸镁纳米花的干燥方程为M_R=exp[-(kt)~n],干燥速率方程为-(dM_R)/(dt)=knM_R(-lnM_R)~((n-1)/n),干燥速率常数k=A exp[(-E_v(1+C_LL))/(RT)],干燥时间指数n=1.738,界面蒸发活化能E_v=16.521kJ/mol,指前因子A=7.214min~(-1),经验常数C_L=29.900 m~(-1)。     

含油污泥为黏结剂制型煤干燥过程研究

为提高干燥效率、优化干燥效果,采用以含油污泥为黏结剂,与粉煤掺混干燥制备型煤的方式对含油污泥进行资源化处理。研究了掺煤量、干燥风速、干燥温度和型煤粒径对干燥过程的影响,并得到含水率和干燥速率随时间变化曲线。结果表明,以含油污泥为黏结剂制型煤的干燥过程可分为三个阶段:升速阶段、等速阶段和降速阶段。掺煤量主要影响降速阶段,风速主要影响升速阶段,温度主要影响升速阶段和等速阶段,粒径主要影响降速阶段。掺煤量越大、风速越大、温度越高、粒径越小,则干燥速率就越大。试验筛选出最佳干燥条件:掺煤量为65%、风速为2.75m/s、温度为105℃、粒径为10mm。对最佳干燥条件下的干燥过程进行干燥动力学模型拟合,求解干燥方程,得出Page(Ⅱ)模型相关系数平方为0.991时,拟合效果较好,能够反应其干燥特性。     

果壳生物质燃烧特性与动力学分析

为充分利用果壳生物质废弃物,采用热重分析对油茶壳、核桃壳、澳洲坚果壳进行了燃烧实验研究,考察了不同升温速率下3种果壳生物质的燃烧特性及动力学参数。结果表明：3种果壳生物质燃烧特性不同,但燃烧特性参数均随升温速率升高而增大;随着升温速率的增加,着火点、燃尽温度、最大燃烧速率、平均燃烧速率及综合燃烧特性指数提高;10℃/min时,油茶壳、核桃壳、澳洲坚果壳综合燃烧特性指数分别为0.56×10^-7、1.18×10^-7、0.88×10^-7;3种果壳生物质的燃烧反应遵循一级反应动力学模型,相关系数（R²）均达0.93以上,低温阶段活化能为30.40~52.41 kJ/mol,高温阶段活化能为18.49~40.62 kJ/mol,低温阶段活化能均大于高温阶段。     

玉米秸秆热解特性及动力学分析

以玉米秸秆为原料, 利用热重分析法研究其热解的特性及动力学。根据TG和DTG曲线, 研究玉米秸秆的热解特性, 采用Flynn-Wall-Ozawa(FWO)和Kissinger-Akahira-Sunose(KAS)两种等转化率法计算玉米秸秆热解的活化能, 并结合主曲线法和Coats-Redfern(C-R)法探讨了玉米秸秆热解遵循的机理方程。研究结果表明: 玉米秸秆热解过程可分为干燥脱水、过渡、主热解和炭化4个阶段, 随着热解升温速率增大, TG和DTG曲线向高温侧偏移; 利用FWO和KAS法计算得到的表观活化能分别为181.7和181.5 kJ/mol; 利用主曲线法和C-R法求解出玉米秸秆热解的机理方程遵循Avrami-Erofeev方程, 当α=0.1~0.5时, n=3, f(α)=1/3(1-α)[-ln(1-α)]^-2; 当α=0.5~0.7时, n=2, f(α)=1/2(1-α)[-ln(1-α)]^-1。     

PA热熔胶颗粒的压缩空气干燥模型

针对塑料工业中塑料颗粒干燥问题，研究了以压缩空气作为风源的热风干燥特性及其数学模型，为聚酰胺(PA)热熔胶颗粒干燥工艺提供参考。采用正交试验探索温度及风压对干燥的影响，比较了11种薄层干燥模型的适用性。结果得出不同风温下的水分有效扩散系数D_eff为1.0×10^-9～3.2×10^-9 m²/s。PA热熔胶颗粒的干燥活化能E_a为36.438 kJ/mol。描述干燥特性的最佳模型为Logarithmic模型，并进一步给出了0.25 MPa风压下与温度相关的干燥数学模型。     

碱式氯化镁纳米棒干燥动力学方程及参数的确定

在不同床层厚度和不同干燥介质温度下，对碱式氯化镁纳米棒进行干燥动力学实验，得到其干燥曲线和干燥速率曲线。采用薄层干燥模型对所得干燥动力学实验数据进行数学处理，得到碱式氯化镁纳米棒的干燥方程为MR=exp[-（kτ）^n]，干燥速率方程为-dMR／dτ=knMR（-lnMR）^（n-1）/n，干燥速率常数k=Aexp[-Ev（1＋CLL）／RT]，干燥时间指数n=1．821，界面蒸发活化能Ev=11．228kJ／mol，指前因子A=4．237min^-1，经验常数CL=55．556m^-1。     

Surface dynamics during latex film formation

Surface dynamics during latex film formation has been investigated theoretically and experimentally by atomic force microscopy. The peak-to-valley distance, y(t), of the latex particles in the surface plane of the latex film decayed exponentially with time during film formation. A theoretical relationship between y(t) and time, t, is given by y(t)=y(0) exp[−t/τ], where y(0) is the value of y(t) when t is zero. τ is a characteristic constant related to the nature of polymer, the particle radius, the surface diffusion coefficient and the temperature. The relationship between the surface diffusion coefficient, D_s, y(0), the radius of the latex particles, R, temperature, T, and τ is given approximately by D_s=1.2×10⁻²⁰y(0)²[2R−y(0)]²T/τ (cm²/s), where the units are manometers for y(0) and R, kelvin for temperature, and seconds for τ. By measuring the decay of y(t) with time, the surface diffusion coefficient can be obtained. The surface diffusion coefficient for a poly(methyl methacrylate-co-butylacrylate) (50:50) copolymer latex film was found to be A×10⁻¹³ cm²/s, A is temperature-dependent.     

Infrared thin layer drying of saffron (Crocus sativus L.) stigmas: Mass transfer parameters and quality assessment

Saffron is the most precious and expensive agricultural product. A dehydration treatment is necessary to convert Crocus sativus L. stigmas into saffron spice. To the best of our knowledge, no information on mass transfer parameters of saffron stigmas is available in the literature. This study aimed at investigating the moisture transfer parameters and quality attributes of saffron stigmas under infrared treatment at different temperatures(60,70, …, 110 °C). It was observed that the dehydration process of the samples occurred in a short accelerating rate period at the start followed by a falling rate period. The effective moisture diffusivity and convective mass transfer coefficient were determined by using the Dincer and Dost model. The diffusivity values varied from1.1103 × 10~(-10)m~2·s~(-1)to 4.1397 × 10~(-10)m~2·s~(-1) and mass transfer coefficient varied in the range of 2.6433 × 10~(-7)–8.7203 × 10~(-7)m·s~(-1). The activation energy was obtained to be 27.86 k J·mol~(-1). The quality assessment results showed that the total crocin content increased, when the temperature increased up to90 °C but, in higher temperatures, the amount of crocin decreased slightly. The total safranal content of the samples decreased slightly when drying temperature increased from 60 °C to 70 °C and then continuously increased up to 110 °C. Also, the amount of picrocrocin increased from 83.1 to 93.3 as the drying temperature increased from 60 °C to 100 °C.     

T型撞击流反应器的微观混合性能研究(英文)

Confined impinging jet reactor (CIJR) offers advantages for chemical rapid processes and has become an important new reactor used in the chemical industry. The micromixing efficiency in a T-shaped CIJR for two tubes of inner diameter of 3 mm was studied by using a parallel competing iodide–iodate reaction as the working system. In this work, the effects of different operating conditions, such as impinging velocity and acid concentration, on segregation index were investigated. In addition, the effects of the inner nozzles diameter and the distance L between the jet axis and the top wal of the mixing chamber on the micromixing efficiency were also considered. It is concluded that the best range of L in this CIJR is 6.5–12.5 mm. Based on the incorporation model, the estimated minimum micromixing time tm of CIJR approximately equals to 2 × 10?4 s. These experimental results indicate clearly that CIJR possesses a much better micromixing performance compared with the conventional stirred tank (micromixing time of 2 × 10?3 to 2 × 10?2 s). Hence, it can be envisioned that CIJR has more promising applications in various industrial processes.     

Effect of Pulsed Electric Field and Osmotic Dehydration Pretreatment on the Convective Drying of Carrot Tissue

The influence of pulsed electric field (PEF) and subsequent centrifugal osmotic dehydration (OD) on the convective drying behavior of carrot is investigated. The PEF was carried out at an intensity of E = 0.60 kV/cm and a treatment duration of t_PEF = 50 ms. The following centrifugal OD was performed in a sucrose solution of 65% (w/w) at 40°C for 0, 1, 2, or 4 h under 2400 × g. The drying was performed after the centrifugal OD for temperatures 40-60°C and at constant air rate (6 m³/h).

With the increase of OD duration the air drying time is reduced spectacularly. The dimensionless moisture ratio Xr = 0.1 is reached for PEF-untreated carrots after 370 min of air drying at 60°C in absence of centrifugal OD against 90 min of air drying after the 240 min of centrifugal OD. The PEF treatment reduces additionally the air drying time. The total time of dehydration operations can be shortened when OD time is optimized. For instance, the minimal time required to dehydrate untreated carrots until Xr = 0.1 is 260 min (120 min of OD at 40°C and 140 min of drying at 60°C). It is reduced to 230 min with PEF-treated carrots.

The moisture effective diffusivity D_eff is calculated for the convective air drying based on Fick's law. The centrifugal OD pretreatment increases drastically the value of D_eff. For instance, 4 h of centrifugal OD permitted increasing the value of D_eff from 0.93 · 10^-9 to 3.85 · 10^-9 m²/s for untreated carrots and from 1.17 · 10^-9 to 5.10 · 10^-9 m²/s for PEF-treated carrots.     

Estimation of Effective Moisture Diffusivity of Okra for Microwave Drying

The effect of microwave output power and sample amount on effective moisture diffusivity were investigated using microwave drying technique on round okra (Hibiscus esculentus L.). The various microwave output powers ranging from 180 to 900 W were used for the determination of effective moisture diffusivity for constant sample amount of 100 g okra. To examine the effect of sample amount on effective moisture diffusivity, the samples in the range of 25-100 g were dried at constant microwave output power of 360 W. By increasing the microwave output powers and decreasing the sample amounts, the effective moisture diffusivity values ranged from 20.52 × 10^-10 to 86.17 × 10^-10 and 34.87 × 10^-10 to 11.91 × 10^-9 m²/s^-1, respectively. The modeling studies were performed to illustrate the relationship between the ratio of the microwave output power to sample amount and effective moisture diffusivity. The relationship between drying constant and effective moisture diffusivity was also estimated.     

Catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O3 in a rotating packed bed

This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al₂O₃ (Cat) in a rotating packed bed (RPB) for the first time. The results showed that the value of the overall decomposition rate constant of ozone (K_c) and overall volumetric mass transfer coefficient (K_La) are 4.28×10^-3 s^-1 and 11.60×10^-3 s^-1 respectively at an initial pH of 6, β of 40, of 60 mg·L^-1 and Q_L of 85 L·h^-1 in deionized water, respectively. Meanwhile, the K_c and K_La values of Fenhe water are 0.88×10^-3 s^-1 and 2.51×10^-3 s^-1 lower than deionized water, respectively. In addition, the K_c and K_La values in deionized water for the Cat/O₃-RPB system are 44.86% and 47.41% higher than that for the Cat/O₃-BR (bubbling reactor) system, respectively, indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.     

QUANTITATIVE ANALYSIS OF DRYING BEHAVIOUR OF FRUITS AND VEGETABLES

In this study, the drying characteristics of seven vegetables (garlic, potato, bean. ginger, leek, onion, and carrot) and five fruits (avocado, banana, sultana, kiwi fruit and apple) were studied under idealised 'constant' controlled drying conditions using an automatic thermogravimetric analyser. Drying-rate curves were constructed and quantified in a systematic way using the least-squares method. This allowed the drying behaviour of each product to be expressed in terms of three variables; gradient of the “constant rate” stage, gradient of the falling rate stage and critical moisture content (CMC)

The drying curves of fruits and vegetables were found to vary greatly indicating the nature of foodstuffs to have a strong effect on the drying kinetics. The gradient of the constant rate period was not truly constant but had an average gradient of 3.1 × 10^-4 per second with bean having the lowest gradient (1.9 × 10 ^-4/) and garlic having the highest gradient (5.3 × 10^-4/s). This was expected as bean had the highest moisture content (93% wet basis) and was able to feed the surface with sufficient water to maintain a near constant rate of evaporation

The falling-rate period ranged from 10 × 10^-4 per second with avocado and garlic having the lowest gradient while apple had the highest gradient of 30 × 10^-4 per second. The CMC for most of the fruits and vegetables studied was about 1 kg/kg dry mass. This means that, at the CMC, the mass of water was the same as the mass of dry matter but with a spread in values from 0.7 for a fruit like banana to 1.8 for avocado.     

Drying Characteristics of Barley Grain Dried in a Spouted-Bed and Combined IR-Convection Dryers

A study was performed to determine the drying characteristics and quality of barley grain dried in a laboratory scale spouted-bed dryer at 30, 35, 40, and 45°C and an inlet air velocity of 23 m/s^-1, and in an IR-convection dryer under an infrared radiation intensity of 0.048, 0.061, 0.073, and 0.107 W cm^-2 at an air velocity of 0.5 m/s^-1. The results show that the first, relatively short, phase of a sharp decrease in the drying rate was followed by the phase of a slow decrease. The time of barley drying depended on temperature of inlet air in a spouted-bed dryer and on radiation intensities in an IR-convection dryer. Barley drying at 45°C in a spouted-bed dryer was accompanied by the lowest total energy consumption. The average specific energy consumption was lower and the average efficiency of drying was higher for drying in a spouted-bed dryer. The effective diffusivities were in the range 2.20-4.52 × 10^-11 m² s^-1 and 3.04-4.79 × 10^-11 m²/s^-1 for barley dried in a spouted-bed and in an IR-convection dryer, respectively. There were no significant differences in kernel germination energy and capacity between the two drying methods tested.