煤泥滤饼碎干工艺的研究

针对湿法选煤生产的煤泥滤饼,提出将其定量破碎后放以穿流干燥,以此调整其块度和水分,满足商品动力煤的质量要求,再与之掺配售出,进而高效益、大批量地解决选煤厂煤泥产品的出路问题。并从理论上分析了穿流干燥作业恒速与降速干燥阶段的影响因素,简要介绍了通过中间试验和工业试验对碎干工艺的研究。     

Heat and Moisture Transfer Model for Onion Drying

Abstract

Onion slices of 3 mm thick were dried in an atmospheric batch tray dryer in order to investigate the influence of air temperature and drying time on parameters such as sample moisture content and drying rate. A model is proposed which takes into account both moisture and temperature distributions in the sample and is in a fair agreement with the experimental data. The models suggested so far by other workers take only the moisture distributions into account for onion drying.     

Heat and Moisture Transfer Model for Onion Drying

Onion slices of 3 mm thick were dried in an atmospheric batch tray dryer in order to investigate the influence of air temperature and drying time on parameters such as sample moisture content and drying rate. A model is proposed which takes into account both moisture and temperature distributions in the sample and is in a fair agreement with the experimental data. The models suggested so far by other workers take only the moisture distributions into account for onion drying.     

Study of Intermittent Low-Pressure Superheated Steam and Vacuum Drying of a Heat-Sensitive Material

Low-pressure superheated steam drying (LPSSD) has recently been applied to drying of various heat-sensitive foods and bioproducts with success. Several studies have shown that the quality of LPSSD-dried products is superior to that obtained using conventional hot air or vacuum drying. However, drying time and energy consumption for LPSSD is generally greater than that for vacuum drying. Therefore, it is necessary to examine different methodologies to improve the energy efficiency of LPSSD. An intermittent drying scheme is one possible method to reduce the energy consumption of the process while maintaining the desired product quality. In this study, the effect of intermittent supply of energy (through an electric heater and steam injection to the dryer) and vacuum (through the use of a vacuum pump) at various intermittency values or on:off periods (10:5, 10:10 and 10:20 min in the case of intermittent supply of energy and 5:0, 5:5, and 5:10 min in the case of intermittent supply of vacuum) at the on-period setting temperatures of 70, 80, and 90°C on the drying kinetics and heat transfer behavior of the drying samples (banana chips) was studied. The effects of these intermittent drying schemes and conditions on the quality parameters of dried banana chips; i.e., color, shrinkage, texture, and ascorbic acid retention, were also studied. Finally, the energy consumption values for intermittent LPSSD and vacuum drying were monitored through the effective (or net) drying time at various intermittent drying conditions and compared with those using continuous LPSSD and vacuum drying.     

Transfer of Phenolic Compounds from Olive Mill Wastewater to Olive Cake Oil

The transfer of the phenolic compounds from olive mill wastewater (OMW) to oil extracted under microwave from olive cake (OC) was carried out by using the following operations: mixing of the olive mill wastewater with the olive cake, drying of the mixture and recovery by solvent of the olive cake oil enriched by phenolic compounds. In the first part of this work, we made a screening design using a Hadamard matrix to quickly locate the factors influencing the process. Among five potentially influential parameters, we found that only three were actually active (OMW/OC ratio noted R, mixing velocity of mixture Vm and mixing time Tm). In the second part, fractional factorial design (2^5?1) was performed to evaluate the effects of five variables (three of them being selected by screening with exposition time Te and radiation power P) and their eventual interactions. The p value (p < 0.05) indicated that R, P,Te, Vm and Tm had significant effects on the response followed by the interaction effects between R‐P, P‐Te, R‐Vm, Te‐Vm, Te‐Tm, and Vm‐Tm. Under optimal conditions, the addition of OMW to OC increased the phenolic compounds content in the oil from 0.04 ± 0.01 to 0.13 ± 0.02 g/L.     

Microwave-Assisted Thin Layer Drying of Wheat

Drying characteristics of Canada Western Red Spring (CWRS) wheat were studied using a domestic microwave convective oven. The effects of microwave power level, grain bed thickness, and initial grain moisture on the drying kinetics were investigated. Wheat samples with initial moisture levels of 0.18 to 0.29 kg water/kg of dry matter were dried for different drying periods of 180 to 360 s. The moisture loss data were recorded at regular short intervals. Then moisture loss data were fitted to various models (Page equation, modified drying equation, and Midilli equation) to study the drying kinetics of wheat. The results showed that wheat moisture loss increased with increasing microwave power level. A mathematical model was developed by coupling mass and energy balances, resulting in a system of non-linear equations. The predicted moisture loss data from the developed model were compared by fitting to experimental microwave data that were in good agreement.     

铬黄滤饼洗涤吹干效果的实验研究

介绍了铬黄滤饼洗涤的重要性及存在的问题,用自制的实验设备及设计的流程,通过正交实验设计,进行了各种工况条件下的实验,取得了相应的实验数据,研究分析得到了洗涤时间、压力、温度对洗涤效果的影响和滤饼吹干时间与滤饼含盐量关系及洗涤时间、压力、温度、吹干等的最佳操作值。     

Modeling Intermittent Drying Using an Adaptive Neuro-Fuzzy Inference System

ABSTRACT

Artificial intelligence systems such as artificial neural networks (ANN) and fuzzy inference systems (FIS) are widely accepted as a technology offering an alternative way to tackle complex and ill-defined problems. The advantages of a combination of ANN and FIS are obvious. This article presents the application of a hybrid neuro-fuzzy system called adaptive-network-based fuzzy inference system (ANFIS) to time dependent drying processes and is illustrated by an application to model intermittent drying of grains in a spouted bed. An introduction to the ANFIS modeling approach is also presented. The model showed good performance in terms of various statistical indices.     

Modeling Intermittent Drying Using an Adaptive Neuro-Fuzzy Inference System

Artificial intelligence systems such as artificial neural networks (ANN) and fuzzy inference systems (FIS) are widely accepted as a technology offering an alternative way to tackle complex and ill-defined problems. The advantages of a combination of ANN and FIS are obvious. This article presents the application of a hybrid neuro-fuzzy system called adaptive-network-based fuzzy inference system (ANFIS) to time dependent drying processes and is illustrated by an application to model intermittent drying of grains in a spouted bed. An introduction to the ANFIS modeling approach is also presented. The model showed good performance in terms of various statistical indices.     

A Combined Experimental and Theoretical Approach to Study Temperature and Moisture Dynamic Characteristics of Intermittent Paddy Rice Drying

Intermittent drying of paddy rice is fully investigated both theoretically and experimentally. A model is developed to describe simultaneous heat and mass transfer for the drying stages and mass transfer for the tempering ones. The model is considered for both cylindrical and spherical geometries. The model excels in considering non-constant paddy rice and air physical properties as well as surface vaporization and convection. The consequent equations are numerically solved with finite-difference method of line using implicit Runge–Kutta. Furthermore, a set of experiments is conducted in a laboratory-scale fluidized bed dryer to estimate the moisture diffusivity of rice and evaluate the effects of different parameters. Two correlations for moisture diffusivity are derived for each geometry based on the experimental results. It is noteworthy that the geometry choice leads to significantly different moisture diffusivities. As a result, the diffusivity values obtained for spherical presentation is 2.64 times greater than that of cylinder. Moreover, the cylindrical model fits the experimental results more precisely, especially for tempering stage (AARD_cyl = 1.03%; AARD_sph = 1.53%). Model results reveal that thermal equilibrium is quickly reached within the first 2 min. Air velocity shows no influential effect on drying upon establishment of fluidized condition. In addition, drying rate is drastically improved after applying the tempering stage. A definition for tempering stage efficiency is also proposed which shows that 3 h tempering will be 80% efficient for the studied case. Rising temperature significantly improves the drying rate, while it does not contribute much in the tempering efficiency.     

Drying of Foamed Biological Materials: Opportunities and Challenges

An overview is provided on hot air drying of foamed materials in a thin layer (foam-mat drying), foam-spray drying, microwave-assisted drying of liquid foams, as well as microwave drying of frozen foams with and without dielectric solid inserts, used as complementary heat sources. In particular, the mechanisms of heat and moisture transport during the drying of foams are identified. The effects of foam characteristics (e.g., foam density and stability) and drying conditions (temperature, air velocity) on drying kinetics and product quality are examined, and the differences between the drying of non-foamed and foamed materials are discussed.     

Changes in Olive and Olive Oil Characteristics During Maturation

Changes in olive properties and oil quality, oxidative stability, phenolic and chemical composition of two common Turkish varieties (Memecik and Edremit) during maturation were investigated. Olive samples were collected in their own growing region for five different harvest dates and processed to oil with a laboratory scale mill. Metabolic behaviors of these two varieties along with the maturation were different in terms of some compositional parameters. Oleic acid, triolein, β-sitosterol, oleuropein, hydroxytyrosol, and tyrosol contents of olive or olive oils fluctuated with maturation. However, changes in average weight, flesh/pit ratio, water and oil contents of the olives were observed. Phenolics such as trans cinnamic acid contents of both olive fruits decreased whereas cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside anthocyanins increased. Free fatty acids of virgin olive oils were found independent of maturity although some slight changes were determined in peroxide value, dien and trien conjugations. Some compositional parameters such as pigment concentration, tocopherols, stearic acid, linolenic acid, palmitodiolein and monounsaturated/polyunsaturated fatty acid ratio decreased while linoleic acid, dioleolinolein, palmitooleolinolein and Δ-5-avenasterol percentages increased with the maturation. A clear discrimination was observed with principal component analysis. The data obtained can also be considered useful for providing information to determine the ideal maturity stage.     

Experimental Study on Microwave Vacuum Drying of Two-Porosity Level Media

Microwave vacuum drying experiments were performed on a laboratory scale dryer with a two-level porosity material: a packed bed of porous alumina beads. The incident microwave power and the vacuum pressure level were fixed, the main varying parameters being the beads diameter and porosity, and the mean pore diameter. The drying kinetics and the evolution of the product temperature are presented. The drying kinetics can be divided into two main periods. The first one corresponds to the drying from the bed voids according to evaporation mechanism that we describe with a stagnant film law. The second one corresponds to the drying from the particle pores and we divide it into two parts: we suggest that the former is dominated by capillarity driven moisture transport, and the latter is limited by the desorption kinetics of the few water layers left.     

Experimental Study on Microwave Vacuum Drying of Two-Porosity Level Media

Abstract

Microwave vacuum drying experiments were performed on a laboratory scale dryer with a two-level porosity material: a packed bed of porous alumina beads. The incident microwave power and the vacuum pressure level were fixed, the main varying parameters being the beads diameter and porosity, and the mean pore diameter. The drying kinetics and the evolution of the product temperature are presented. The drying kinetics can be divided into two main periods. The first one corresponds to the drying from the bed voids according to evaporation mechanism that we describe with a stagnant film law. The second one corresponds to the drying from the particle pores and we divide it into two parts: we suggest that the former is dominated by capillarity driven moisture transport, and the latter is limited by the desorption kinetics of the few water layers left.     

Drying of Droplets Containing Insoluble Nanoscale Particles: Second Drying Stage

A theoretical model describing the second drying stage of a droplet containing a liquid with insoluble nanoscale primary particles is presented. The model enables two possible pathways for the evolution of the particle morphology, leading to the formation of either a full solid particle or a hollow particle containing internal aggregates. It was found that the final morphology of the dry particle depends on the size of the suspended primary particles, the strength of the particle crust, the initial moisture content, and the parameters of the drying agent. The formation of a hollow particle morphology is more likely for smaller primary particles and stronger inter-particle forces.     

Intermittent drying of initially saturated porous materials

The aim of this paper is to examine the advantages of convective non-stationary (intermittent) drying and the possibility of its application to materials susceptible to crack formation (wood and ceramics). The notion “non-stationary” means here drying with periodically changeable parameters (air temperature and humidity). The drying time, energy consumption, and quality of dried samples are examined at different schedules of intermittent drying. The acoustic emission (AE) method is applied to monitor on line the material behavior and to detect the commencement of material cracking, and thus to find the moment at which the changes in drying conditions should be initiated. The mathematical model is developed to describe and imitate the intermittent drying kinetics determined experimentally. This model is used next for numerical calculation of the net energy used for drying, and to compare it with the measured total electric energy consumption. The tests were carried out on cylindrically shaped samples of wood and kaolin-clay. The benefits of non-stationary drying with respect to that performed in constant conditions were assessed. Such a formulated subject is a novelty in drying area.     

石灰调质污泥恒温干燥特性及动力学模型研究

对添加石灰的市政污泥进行恒温干燥实验,研究在不同的石灰添加量和不同的温度条件下污泥干燥特性、有效水分扩散系数和干燥活化能。结果表明:高温干燥时,石灰添加量的增加对平均干燥速率以及有效扩散系数的提高影响显著,低温干燥时影响不显著;石灰的添加可以降低干燥活化能;基于Modified Page模型建立的通用干燥模型能准确地描述石灰调质污泥的干燥特性;模型方程预测值和实验值吻合,均方根误差为0.32%。     

Effects of Operating Conditions on the Combined Convective-Microwave Drying of Agar Gels

Combined convective-microwave drying enables a considerable reduction in drying time compared to convective drying, the time required for the process being inversely proportional to the microwave power applied. This work presents the convective-microwave drying experiments carried out using agar gel plates conducive to studying the influence on drying kinetics of parameters such as the microwave power applied, sample thickness, and air conditions (humidity, temperature, airflow).