Effect of the insulation and the material of the inclined sheet on the drying of anhydrous lactose in a continuous vertical fluid bed dryer (original) (raw)
Related papers
Drying of aqueous lactose solutions in a single stream dryer
Food and Bioproducts Processing, 2008
Spray-dried lactose is a useful ingredient in many food and drug preparations. In the literature, many articles have attempted to mathematically characterize the drying kinetics and the product quality during spray drying of various dairy products using a number of approaches. As far as lactose is concerned, little mathematical analysis is available regarding its detailed drying kinetics. Recently, the reaction engineering approach (REA) was found to be useful to formulate a drying kinetics model for drying of aqueous lactose droplets. The main objective of this work is to determine the sensitivity of the REA in order to assess its performance over different drying and feed conditions, which may be relevant to an industrial scenario. A single stream drying (S 2 D) approach was used for modeling the air-drying of aqueous lactose droplets, as this technique is simple to be used and reduces the computation time. Some laboratory results on the physical characteristics of the air-dried lactose particles are also reported using the S 2 D approach.
2008
In drying operation the material characteristics such as heat sensitivity, moisture content and particle size are of great importance, which should be taken into account in selection of proper design and conditions for the process. Rigorous quality requirements, i.e. gentle drying of heat sensitive materials, stable, well-controlled and economic operation can be fulfilled by using Mechanically Spouted Bed (MSB) dryer with inert particles developed to eliminate some drawbacks of the conventional spouted bed dryers. In this paper the construction and the main features of MSB-dryer are presented. Different tasks with special quality demands, namely drying of bovine serum albumin and moisture removal from tomato pulp of thermoplastic behaviour, and a method to accomplish these requirements are shown.
Performance analysis of cassava starch drying in continuous vibrated fluidized bed dryer
This paper presents the energy and exergy analysis of cassava starch drying in continuous vibrated fluidized bed dryer. Experiments were performed at temperature 50, 60, and 70 o C, feeding rates of 0.17 and 0.5 g/s, and weir height of 0 and 10 mm in a constant air velocity of 4.5 m/s. The results show weight loss of dried sample is 30–76%, final moisture content is 2.4–13.8%, drying efficiency is 34-89%, energy efficiency is 2–21%, and exergy efficiency is 7–86 %. Both energy and exergy analysis increased with increasing of temperature.
Assessment of Dryer Performance Under Intermittent Drying of Grains in Fixed Bed
Engevista, 2017
Intermittent drying is an operation that aims to improve drying process performance with modulations of inlet air conditions such as its temperature and velocity, contrary to the conventional operation, in which air conditions are constant. This alternative operation aims to determine the best modulation pattern of air conditions to minimize energy consumption, maximize dryer performance or improve material quality. In this context, the objectives of this work are to simulate the drying process of some grains in fixed bed and assess if it is possible to enhance the dryer performance in terms of drying rates under intermittent operation in comparison with results obtained with conventional operation. Both intermittent and conventional operations were simulated with the same energy consumption related to the energy supplied by the air at the dryer entrance. Results revealed that the drying rates were higher under intermittence of inlet air temperature in comparison with results obtain...
Convective Drying in the Multistage Shelf Dryers: Theoretical Bases and Practical Implementation
Drying Unit Operations [Working Title]
The main advantages regarding the convective drying of the granular materials in the multistage dryers with sloping perforated shelves were represented. Peculiarities of the shelf dryers' hydrodynamics were shown in the research. Various hydrodynamic weighing modes were experimentally justified, and the relevant criteria equations were obtained. The results of investigations regarding the interphase heat and mass transfer were given; criteria dependencies, which predict heat and mass transfer coefficients in the shelf dryers, were proposed. A method to assess the efficiency of the dehydration process at the separate stages of the device and in the dryer, in general, was proposed. The algorithm to define the residence time of the granular material on the perforated shelf with a description of the author's software product for optimization calculation was shown. The shelf dryers' engineering calculation method was presented in this work. The original constructions of devices with various ways to control the residence time of the granular material that stays in their workspace were described. The testing results of the shelf dryer to dry granular materials, such as coarse-and fine-crystalline potassium chloride, sodium pyrosulfate, and iron and nickel powders, were demonstrated.
Experimental study of drying kinetics of skim milk
Drying kinetics of skimmilk solution is investigated in thiswork. Dry oven method used to determine the characteristic drying curves. The experiments are carried out at two temperatures of 45Cand 60C and three different initial solid contents. The obtained characteristic curves for drying rate are normalized, based on a simple mass transfer model in which the drying rate is considered as a first order reaction. These normalized curves are independent of temperature and initial concentration and coincide together. The obtained experimental data are applied to identify a simple mass transfer model parameter. Finally a relative humidity factor f, is obtained as a function of , characteristic moisture content. This model can be used in CFD modeling of spray dryers for simple and efficient calculations.
Chemical Engineering and Processing - Process Intensification, 2018
Several spouted bed configurations have been proposed in order to overcome the limitations and disadvantages of the conventional spouted bed (CSB). This paper evaluates the performance of a modified mechanically spouted bed (MMSB) fitted with a helical screw, which was applied in the drying processes of alumina and skimmed milk. In this equipment, the cyclic movement of the solid phase was promoted by the screw and the air was supplied perpendicularly, following the CSB design. The main objective of this study was to analyze the energy performance of the MMSB. The results showed that the MMSB provided a drying process under stable conditions at air velocities lower than the minimum spout velocity, due to inclusion of the helical screw, leading to greater energy efficiency and lower energy consumption.
Spray Drying and Crystallization of Lactose with Humid Air in a Straight-Through System
Drying Technology, 2014
The effects of different humidities on process yields and degrees of crystallinity have been studied for spray-dried powders from the spray drying of lactose with humid air in a straight-through system. According to Williams-Landel-Ferry (WLF) kinetics, it was suggested that a higher particle temperature and lower glass transition temperature would increase the crystallization rates of the particles during the spray-drying process. Freshly humidified air produced by a Buchi-B290 spray dryer as a humidifier before the main spray dryer decreased the particle glass transition temperature (T g ), while allowing the particle temperature (T p ) to reach higher values by using an insulated drying chamber. The results showed that higher T p À T g , as a result of applying humid air, improved the process yield from 21 AE 4% to 26 AE 2% and the lactose crystallinity by decreasing the latent heat of crystallization for the powder products from 43 AE 1 J/g to 30 AE 11 J/g. It has been found in this study that the humidity of the inlet air should be adjusted in such a way as to not exceed relative and absolute humidities of 2.7-3% and 65-70 g/kg DA , respectively, at the outlet of the drying chamber, to give the most crystalline particles.
Thermal analysis in fluidized bed drying of moist particles
Applied Thermal Engineering, 2002
This paper deals with thermal modeling of the fluidized bed drying of wet particles to study heat and mass transfer aspects and drying thermal efficiencies. The model is then validated with the literature experimental data obtained for corn. A parametric investigation is undertaken to study the effects of the inlet air temperature, the air velocity and the initial moisture content of the material (i.e. corn) on the process thermal efficiency. The results show that the thermal efficiencies of the fluidized bed drying decrease sharply with decreasing moisture content of corn and hence increasing drying time, and apparently become the lowest at the end of the drying process. This clearly indicates that the moisture transfer from the material depends strongly on the air temperature, air velocity and the moisture content of material. A good agreement is obtained between the model predictions and the available experimental results.
EXPERIMENTAL EVALUATION OF A FLUIDIZED BED DRYER PERFORMANCE
Results of an experimental study on the drying characteristics of fluidized bed dryer are presented. The experimental rig comprises of the air blower, heater, drying chamber and chimney. The materials used in the drying study were; cassava, yam and maize. The drying experiments were carried out according to the following parameters: initial moisture content of the material (High and Low), drying time and various optimum temperatures. The results obtained show that it took a total of 150minutes with an optimum temperature of 60 o C to reduce the moisture content of the cassava and yam from 75.4%(w.b) to the equilibrium moisture content of 11% which is suitable for storage and preservation while maintaining the external conditions. While the optimum temperature that gives faster drying time for maize was 40 0 C. Similarly, a preliminary sun drying experiment was carried out to ascertain the drying time of the cassava and yam chips. It was observed that in the case of sun drying of cassava, it takes a total of 72hrs with an average ambient temperature of 30 o C to reduce the moisture content from 75.4 % (w.b) to the equilibrium moisture content of 11 % (w.b). Similarly, the effect of temperature at 30 0 C on the drying curves for the maize shows that the value of the constant rate period of the experiment was smaller than the value obtained at the temperatures of 35 0 C and 40 0 C respectively. The drying rate of products below their optimal temperature was affected by the lower rate of moisture removal and the equilibrium moisture content by mass was high. While drying at temperatures above the optimum temperature, ultimately may cause the thermal degradation of the products been dried. This could be in form of physical defects, such as, decoration, cracking, shrinking and non-uniform drying. From the drying kinetic curves and visual observations during the experiments, it could be concluded that the fluidized bed dryer is an alternative for the processing of cohesive solids that preserve the final quality of the dry solids.