Cylinder Dryer Research Articles

Fast drying of cut tobacco in drop tube reactor and its effect on petroleum ether tobacco extracts

ABSTRACTEntrained flow drying is an important fast drying tool in tobacco industry. This study used a drop tube reactor (DTR) as an entrained flow dryer to investigate drying process of flue-cured cut tobacco. Lab-scale cold and hot DTRs were set up to obtain drying kinetics for three types of cut tobacco using different drying gases and temperatures. The effective diffusion coefficients of cut tobacco in DTRs were compared with those in a general cylinder dryer. Moreover, the effects of different drying gases and temperatures on petroleum ether extract content were investigated. The results showed that the effective diffusion coefficients of cut tobacco in the DTRs were between 2.296 × 10−8 and 8–6.244 × 10−8 m2/s, which are two orders of magnitude higher than those in the cylinder dryer. Compared to hot air as a drying medium, superheated steam improved the effective diffusion coefficient of cut tobacco. The petroleum ether tobacco extract had a higher retention ratio when the superheated steam was used in the DTRs. An increase in the drying temperature resulted in a lower retention of the petroleum ether tobacco extract.

Condensation heat transfer characteristics and flow regime in a horizontal rectangle channel of a multichannel cylinder dryer

ABSTRACTThe present study investigates the phenomenon of steam condensation in a rectangle horizontal channel with a mass flux range of 20–70 kg/m2/s and a vapor quality of 0.2–0.8. Mass flux and vapor quality were presented to primarily affect the heat transfer coefficient in shear-dominated flow regime, such as the mass flux is greater than 40 kg/m2/s. At the low mass flux, only slug flow, plug flow, and wave flow were observed. At the high mass flux, the wave flow and annular flow were observed even at the low-vapor quality, and the slug and plug flow were not found during the entire condensation process. Observed flow patterns agreed with Tandon’s flow pattern map. Four kinds of correlations are employed to predict the condensing heat transfer coefficient, and the result reveals that Cavallini’s correlation agrees with the experimental results relatively well. The measured pressure drop has a good agreement with the Lockhart–Martinelli correlation.

Study on the Influence of Structural Parameters of Multi-channel Cylinder Dryer on Heat Transfer Performance

Study on the Influence of Structural Parameters of Multi-channel Cylinder Dryer on Heat Transfer Performance

Variation of Steam Velocity in the Channel System of a Drying Cylinder

The movement of condensate droplets in the channel of a drying drum is considered. The dependence of the critical droplet radius on steam velocity in the channel is calculated. Conclusions are drawn regarding the limits of the most appropriate steam flow velocity.

Development of an Energy-Saving Cylinder Drying Machine for Dispersed Moist Materials

Here the question of means for drying dispersed moist materials by directed admission of infrared radiation is considered, and a schematic of the proposed drying machine is given.

Visualization Study of Steam Condensation in Rectangular Channel of Multichannel Cylinder Dryer

The phenomenon of steam condensation occurring on one surface in a rectangular horizontal channel was experimentally studied. The experiment was conducted using a visualization method with a steam quality of 0.1–0.9 and mass flux of 20–50 kg/m2 s. Four flow patterns (annular, wave, slug, and plug) were observed, and the effects of quality and mass flux on the condensing heat transfer were analyzed. The mass flux and steam quality primarily affect the condensing heat transfer coefficient in the shear-dominated flow regime. The condensing heat transfer coefficients are nearly constant only in a certain range of steam quality. This result is disparate from what has been reported in previous literatures. It was also observed that the condensing heat transfer coefficient rises with an increase in the quality. Two flow regime maps were employed to predict the flow regimes observed in this study. The result reveals that the Tandon flow regime map agrees quite well with the experimental results.

Moisture transfer modeling during solar drying of potato cylinders considering shrinkage

ABSTRACTIn the present work, the thin layer drying kinetics of potato during natural convection solar drying was investigated experimentally. Cylindrical potato samples with length 50 mm and varying diameter of 8, 10 and 13 mm were dried in an in-house designed and fabricated laboratory scale mixed-mode solar dryer. Thirteen different thin-layer mathematical models were fitted to the experimental moisture ratio (MR) data. The obtained results indicated that the Modified Page model could satisfactorily describe the drying curve of potato cylinders with higher value of R2 and lower values of RMSE and χ2. The shrinkage parameter is incorporated in the analytical diffusion model to study the moisture transfer mechanism of potato cylinders. It was observed that the values of effective diffusion coefficient (Deff) and convective mass transfer coefficient (hm) are overestimated in the range of 85.02–90.27% and 39.11–45.11% for the range of sample diameter examined, without considering the shrinkage effect in the mass transfer analysis. A Multiphysics approach was adopted in this study to get insight into the drying behavior of potato cylinders in terms of food-moisture interactions during the solar drying process. The predicted results of MR are in close agreement with the experimental data. Moreover, the anisotropic behavior of shrinkage as well as the moisture distribution inside the potato cylinder was very well described by Multiphysics model.

목재수축률 측정에 대한 총설

본 논문에서는 목재 수축률에 관한 1976-2015년도에 발표된 목재공학회지 논문을 정리하였다. 국내산 낙엽송(Larix kaempferi) 수축률을 측정한 연구자들간에 접선방향 수축률은 4.21%-9.79%, 방사방향 수축률은 2.09%-4.67%, 섬유방향 수축률은 0.17%-0.33%로 접선방향 2.3배, 방사방향 2.2배, 섬유방향 1.9배로 연구자들마다 측정 값에 차이가 나타났다. 소나무(Pinus densiflora) 시편 크기가 <TEX>$20{\times}20{\times}20mm$</TEX>에서 <TEX>$100{\times}100{\times}100mm$</TEX>로 증가함에 따라 접선방향, 방사방향, 부피수축률은 2.61%, 1.32%, 0.80% 감소하였다. 아피통(Dipterocarpus grandiflorus)을 밀폐건조, 오븐건조, 실온건조 하였을 때 부피수축률은 31.6%, 26.5%, 21.0%로 건조방법에 따라 5.5%-10.6% 차이가 나타났으며 건조온도가 <TEX>$115^{\circ}C$</TEX>, <TEX>$120^{\circ}C$</TEX>, <TEX>$125^{\circ}C$</TEX>로 증가함에 따라 낙엽송의 수축률은 일정한 증가, 감소 경향이 보이지 않았다. <TEX>$20mm^3$</TEX> 크기의 삼나무(Cryptomeria japonica) 시편을 한국산업규격(KS F 2203, 2004)에서 제시하는 정밀도 0.01 mm의 길이측정도구로 수축률을 측정하였을 때, 방사, 섬유방향 수축률 측정오차는 1.97%, 35.7%로 크게 나타났다. 목재의 수축률은 시편 크기, 건조방법, 측정방법에 영향을 받는 것으로 나타났다. The goal of this study was to review the wood shrinkage published in Journal of The Korean Wood Science and Technology from 1976 to 2015. Previous studies reported that shrinkage from Larix kaempferi in the tangential, radial, longitudinal directions ranged from 4.21%-9.79%, 2.09%-4.67%, 0.17%-0.33%, respectively. When different drying methods including closed cylinder drying, oven drying, and room temperature drying were used, volumetric shrinkage of Dipterocarpus grandiflorus was different, ranging from 31.6% to 21.0%. With an increment of the drying temperature of <TEX>$115^{\circ}C$</TEX>, <TEX>$120^{\circ}C$</TEX>, <TEX>$125^{\circ}C$</TEX>, the shrinkage of Larix kaempferi did not show a consistent trend. When sample size of Pinus densiflora was increased from <TEX>$20{\times}20{\times}20mm$</TEX> to <TEX>$100{\times}100{\times}100mm$</TEX>, the tangential, radial and volumetric shrinkage decreased 2.61%, 1.32%, 0.80%, respectively. When a caliper having a sensitivity of 0.01 mm was used to measure <TEX>$20mm^3$</TEX> specimen from Cryptomeria japonica, the measurement error occurred 1.97% in the radial direction and 35.7% in the longitudinal direction. From the previous studies, wood shrinkage could be influenced by sample size, drying method and measurement technique.

Syngas as an Additional Energy Carrier in the Pulp and Paper Industry: A Mill-Wide System Analysis of a Combined Drying Concept, Utilizing On-Site Generated Gas and Steam

Large amounts of thermal energy are required for different unit operations in the pulp and paper industry. Typically, this energy is distributed by means of steam. In this study, introduction of in-situ-generated syngas as an energy carrier in parallel to the predominant steam has been investigated. The examined systems use dual fluidized-bed gasification integrated with a solid fuel boiler of a paper mill together with impingement drying in combination with cylinder drying, a concept enabling higher specific drying rates. The studied systems exhibit reduced overall energy use when compared to the present situation with conventional steam-heated cylinder drying. Cold tar cleaning by condensation/absorption and firing of the syngas in a gas turbine followed by utilization of the exhaust gases for drying are interesting options because this results in reduced biomass consumption with maintained power production.

The Temperature-Online-Measuring and Energy-Saving System for Drying Cylinder Based on Network Communication

During the process of drying fabrics by drying cylinder dryer, the over-drying of fabrics leads to a waste of energy. A temperature-online-measuring and energy-saving system for drying cylinder dryer based on network communication was designed in the study. The temperature-measuring and steam-controlling part of the system set in the cylinder dryer communicates with the remote monitoring part using the W5100 network chip through Ethernet which helps to achieve a high-speed and long-distance communication between the two parts. The remote monitoring part of the system is based on Delphi. The real-time temperature of fabrics in each drying cylinder can be displayed on the screen of the remote computer, and the steam supply of drying cylinders can be manually or automatically adjusted according to the mutations of temperature of fabrics by system administrators or the remote computer. The application of this system helps to avoid the The evaporation of water due to over-drying by 5.3%-6.6% and result in a reduction of the waste of energy by about 10%.

Research on drying of rapeseed with cylinder dryer type CD-100

Research on drying of rapeseed with cylinder dryer type CD-100

ANSYS Analysis of Heat Model for the Electromagnetic Drying Cylinder

In this thesis, the process of electromagnetic drying cylinder was analyzed creating by the dryer finite element model using ANSYS. The conduction thermal analysis, the applied load and solved showed the results of three major components. Which create a finite element model of the process, mainly the preprocessor using ANSYS software to create or import geometric models from other software applications, and then add the material properties. The last of the geometric model meshing and solving process need to enter solvers according to the actual situation. The setting is applied to the thermal load and conditions. Then it is proceed to the finite element solution operator. It final usually the Post 1, or Post2 view results, and based on our experience to judge correctly

On-site evaluation method for the nonstick properties of paper machine drying cylinder coating materials—A description of the methodology and two case studies

Paper raw materials contain impurities, such as waxes, coating binders, hot melts and pressure-sensitive adhesives, that have a tendency to attach to the surfaces of machinery during paper production. Drying cylinders located at the beginning of the drying section are in an especially challenging position because sticky materials can easily transfer from the paper web to the hot cylinder surfaces at this point.Usually, one to four drying cylinders are coated with a nonstick coating material in order to decrease contamination. The nonstick properties of coating materials are at their best when the coatings are new, but their performance usually decreases as the materials age. To date, there is no practical method available for the on-site evaluation of the nonstick properties of coating materials or a method to monitor the condition of the coating during its life cycle.A new practical method for the on-site evaluation of nonstick cylinder coating materials has been developed. This method also provides the opportunity to compare the performance of different drying cylinder coating materials. The analysis is performed using an adhesive tape attached to a clean cylinder surface. The tape is immediately peeled off of the surface at a constant speed and peel angle. The temperature compensation is used to facilitate the comparison of surfaces at different temperatures. The force required to peel off the adhesive tape is monitored with a force meter. Our results show a linear relationship between the release force and the nonstick qualities of the coating.In this paper, a method for testing drying cylinder coatings and the results of mill tests are presented.

Modification of cell structure and mass transfer in potato tissue by contact ultrasound

The application of contact ultrasound in food drying processes can increase drying rates of fruit and vegetable products. In order to get a deeper understanding of the mechanisms involved this study dealt with the analysis of changes in tissue structure and mass transfer in potato (cultivar Belana) during a contact ultrasound treatment. Individual potato cylinders were sonicated on a stainless steel screen that served as sample supporting and sound transmitting surface. Cell injury and water content were analyzed in different tissue layers in dependence of sonication time and intensity. Although ultrasound related cell disruption was limited to a thin tissue layer in direct vicinity to the sonicated surface, mass transfer was influenced throughout the complete sample cylinder with a height of 1cm. The improved water removal from the product could thus be attributed to ultrasound effects affecting mass transfer at tissue level, e.g. microstirring, reduction of boundary layers, sponge effect, absorption heating and structural changes. Ultrasound effects observed at ambient conditions could be transferred to convective drying of potato cylinders at 70°C.

Innovative Design for Supply Mode of Steam in Drying Cylinder

This paper analyzed the dynamic state of the water ring, which is formed through the exothermic process of steam condensation, and its influence on heat transfer during the operating process of the high speed paper machine’s drying cylinder. The influence of perturbation on the flow condition of the water ring was also discussed. This information was used to design the steam-knife gas supply system in the drying cylinder. This system provides a so-called steam-knife to attack the water ring, which would change the dynamic state of the water ring’s fluid level. This would ultimately improve the heat transfer efficiency.

On Structure and Heat-Transfer Mechanism for Multi-Channel Drying Cylinder of Energy-Saving Type

In this paper, the authors explore the structure and operating mechanism of the energy- saving type multi-channel drying cylinder, which can be used in papermaking machine dryer section to effectively reduce the amount of condensate water, and tackle such problem as the water condensation in drying cylinder. This paper theoretically expatiates upon the heat transfer mechanism of the multi-channel drying cylinder of energy-saving type and verifies the theoretical results with numerical simulation approach, which proves that energy-saving type multi-channel drying cylinder can effectively improve the heat transfer efficiency, and increase the productivity of the papermaking machine while the drying cylinder is featured by high cost in manufacturing and non-uniformity in surface temperature because of its peculiarity of configuration, which need to be investigated and improved.

Flow and Thermal Characteristics of Condensing Steam in a Single Horizontal Mini-Channel of a Multiport Cylinder Dryer

In papermaking processes it is well known that the dryer uses the greatest amount of energy and has costly components compared with other devices. These dryers thus offer outstanding opportunities for energy savings and cost reduction. Recently, Argonne National Laboratory developed the concept of a multiport cylinder dryer in which the steam flows through “ports,” or longitudinally oriented mini-channels, which are close to the cylinder–dryer surface. It was reported that the innovative design minimized the condensate layer thickness and increased the dryer shell's surface temperature. However, no systematically obtained experimental data are available. In this study we conducted experiments to investigate the flow and thermal characteristics of condensing steam in a single horizontal mini-channel, which represents a part of a multiport cylinder dryer. Based on the results, the flow pattern through a single horizontal mini-channel is presented. Also, we observed that the condensing heat transfer coefficient in the single horizontal mini-channel was about seven times higher than that of a conventional dryer with spoiler bars. Finally, the effects of the steam mass flux, system pressure, and aspect ratio of the mini-channel on the average condensing heat transfer coefficients as well as the pressure drops are presented.

Modeling of Batch Dryers for Shrinkable Biological Materials

Design of dryers for biological materials is a complex problem, since in order to solve the model equations, foodstuff physicochemical and equilibrium properties and drying kinetics should be included as a function of water content and operating variables. Shrinkage of biological materials under dehydration must also be taken into account when the macroscopic balances in the bed of drying need to be solved. The main objective of this work was thus to develop a realistic simulation model to predict batch deep bed drying of shrinkable biological materials. Differential macroscopic balances for heat and mass transfer in the air and solid phases were expressed in moving coordinates in order to solve the problem of particle shrinkage during drying. The equation system was solved by the ‘method of lines’ using the Gear package for temporal derivatives and finite differences for spatial ones. All the parameters and physical properties required to solve the model were taken from literature or determined independently in lab-scale experiments. A pilot-scale hot air batch dryer was built in order to carry out experimental determinations during drying of slices or cylinders of potato, apple, and carrot at diverse hot air conditions. The appropriate choice of numerical method and initial conditions gave a reliable and stable solution of the equation system. The simulation results agreed closely to experimental data on deep bed batch drying of food particles under different conditions. The use of variable porosity and volume due to shrinkage during drying improved notably the predictions of the simulation model.

Mathematical modeling and simulation of batch drying of foods in fixed beds with airflow reversal

A mathematical model based on the heat and mass transfer mechanisms between the air and the product was developed in order to simulate the fixed bed drying process of foods conducted with and without periodical reversals of the airflow direction. The proposed model considers the fixed bed of the product as a series of ideal stirred stages connected in series, and was validated with the experimental data obtained during the packed bed drying of carrot cylinders with various times of application of the airflow reversals (15 min, 30 min, and without air flow reversal). The drying experiments were performed using an air velocity of 2 m/s and two different particle thickness/bed height combinations (0.001/0.05 and 0.01/0.1 m/m) at the air temperatures of 50 and 70 °C. A good agreement was found between the experimental and the predicted data. Furthermore, the results showed that the proposed model is able to predict the distributions of moisture content and temperature within the packed bed of the food and a higher frequency of application of the airflow reversal promote slightly shorter drying times and flatter moisture and temperature profiles in the bed than those obtained without it.

Modelling convection drying of blanched parsley root slices

The mathematical model describing the drying curve of single blanched parsley root slices (not touching each other) under conditions of natural convection was formulated on the basis of the general theory of heat and mass transfer laws. The course of the drying curve was described in two ways: (1) using the linear model of the first drying period (without shrinkage) with a model of the second drying period and (2) using the model of first drying period considered for shrinkage with the model of second drying period. Two models for shrinkage were analysed: linear and exponential. The second drying period was described by two models which approximated the shape of dried particles to an infinite plane and finite cylinder. Mathematical models of the first and second drying period were verified using the experimental data. The drying of 3 mm-thick parsley root slices was examined at an air temperatures of 60 °C. Before drying, the slices were blanched by the following methods: 3 min in boiling 5% brine solution, 3 min in boiling water, and 6 min in boiling water. The verification confirmed that the following mathematical models describe the drying curve with satisfactory accuracy: the linear model or models with shrinkage in the first drying period and the model of a finite cylinder in the second drying period. The values of relative error were not higher than 1% for linear model, 10% for models with shrinkage, 40% for models of the finite cylinder drying. The correlation between the data obtained from mathematical models and empirical data was high (the correlation coefficient varied from 0.97 to 0.99).