Industrial Drying Research Articles

Dynamic Modelling of Low-Temperature Batch In-Bin Drying of Cobed Seed Maize: an Industrial Case Study

In this paper, dynamic models have been developed to predict the air temperature, specific humidity and drying rate in an industrial seed grain dryer. An industrial dryer was utilised for experimental measurements. The dyer was modelled as a system of serial cells characterised by heat and mass transfer with air back-mixing. Model equations were solved numerically based on the Levenberg–Marquardt algorithm in MATLAB. The model response was optimised by signal matching technique. The sensitivity of the model parameters on the prediction accuracy was assessed using Monte Carlo simulation tests. The accuracy of the models was statistically checked using the coefficient of determination (R2), the root mean square error (RMSE), and the probability value (p value) approach. The results revealed a good agreement between the measured data and model predictions with the highest mean relative deviation (MRD) of 2.37% and p value of 0.0298 at 5% significance level. The model accuracy was highly sensitive to the parameter that defines the air residence time inside the drying bin. The dryer exhibited air back-mixing level of 45.8% and moisture decay rate constant (k) of 0.028 per hour. The convective heat transfer between the air and seed grain was determined as 0.96 kJ/h m2 °C. The dynamic models developed here can adequately predict the outlet air temperature, specific humidity and solids temperature and subsequently the drying curve. The models could help to provide real-time insights of drying characteristics, which is necessary for the achievement of a stable and effective control of the drying process.

Comprehensive Research on Application and Optimization of Heat Storage Technology Under Different Industrial Demand: Based on Medium and Low Temperature

<p>Heat storage technology is one of the key technologies in the field of solar thermal power generation and cogeneration. It uses heat storage materials as the media to store solar thermal energy, industrial waste heat, low-grade waste heat and other kinds of thermal energy, and release it when needed, so as to solve the mismatch between energy supply and demand. This paper introduces the classification and characteristics of heat storage technology, analyzes the research progress of heat storage technology in the fields of solar thermal power generation, heat storage materials and industrial drying, and forecasts the development trend of heat storage technology in the future. The results indicate that heat storage technology is beneficial to improve industrial production efficiency, broaden industrial energy conservation and emission reduction ideas, and has a great application prospect under the continuous improvement of practitioners with innovative spirit.</p>

Experimental and numerical study on drying behavior of CORN grain

Tower type grain dryers are widely used in corn drying process and are manufactured as cylindrical structures with a height of about 30 m. Grain is filled into the annular section between the perforated walls and dried with exhaust gas from the combustion chamber. In terms of drying quality and energy efficiency, high capacity drying systems need a reliable control system. In the current study, a laboratory scale test prototype of this type of industrial grain dryer is installed to determine the most suitable model to be used in the control system. A fixed bed design has been made that allows hot exhaust gases to enter the drying chamber horizontally, as in industrial tower dryers. Corn drying experiments were carried out experimentally to reveal and model the drying behavior of corn, to examine the effect of air velocity on pressure drop and drying, to show the usability of equations commonly used in the literature. Drying gas temperature is kept constant at 103 °C and inlet gas velocity values are changed to find out velocity effects on pressure drop and drying behavior. Experimental data are modeled with a curve fitting method using MATLAB software. Lewis, Page, Henderson and Pabis, Logarithmic, Midilli and Wang and Singh models, which are known as thin-layer models in the literature are used. The effect of drying air velocity on the coefficients of the best thin layer drying model was determined. Results show the most suitable model is the Midilli model. The obtained results are given in comparison with the results in the literature and a model is proposed for use in control of industrial dryers.

Energy and Exergy Analyses of a Combined Infrared Radiation-Counterflow Circulation (IRCC) Corn Dryer

Energy consumption performance evaluation of an industrial grain dryer is an essential step to check its current status and to put forward suggestions for more effective operation. The present work proposed a combined IRCC dryer with drying capacity of 4.2 t/h that uses a novel drying technology. Moreover, the existing energy–exergy methodology was applied to evaluate the performance of the dryer on the basis of energy efficiency, heat loss characteristics, energy recovery, exergy flow and exegetic efficiency. The results demonstrated that the average drying rate of the present drying system was 1.1 gwater/gwet matter h. The energy efficiency of the whole drying system varied from 2.16% to 35.21% during the drying process. The overall recovered radiant energy and the average radiant exergy rate were 674,339.3 kJ and 3.54 kW, respectively. However, the average heat-loss rate of 3145.26 MJ/h indicated that measures should be put in place to improve its performance. Concerning the exergy aspect, the average exergy rate for dehydration was 462 kW and the exergy efficiency of the whole drying system ranged from 5.16% to 38.21%. Additionally, the exergy analysis of the components indicated that the combustion chamber should be primarily optimized among the whole drying system. The main conclusions of the present work may provide theoretical basis for the optimum design of the industrial drying process from the viewpoint of energetics.

Characterization of drying behavior and modeling of industrial drying process

The general method for industrial chamber dryer optimization was reported in this paper. The first step in finding the most suitable drying regime is to characterized the clay raw material, especially its water loss at 2000C and to determine the critical drying rate inside the specially constructed laboratory dryer. These data provides us information if the product or the dryer is the bottleneck for the optimisation. If the optimization is justified geometry of the dryer, air mass flows, temperature, and humidity profiles inside the dryer as well as initial water content in the drying material, initial temperature of the products and the load of the dryer are required. Some of the previously mentioned data are only used to check if the chamber dryer is working properly, while the others are used as the initial parameters necessary for software simulation. In this paper two models for calculating the optimal drying parameters were used. The first model was developed from the comprehensive theory of the moisture migration during isothermal drying. The calculation software for setting up the non - isothermal drying regimes was reported in our previous papers. It is important to say that this model was not able to adequately predict the temperature raise within the drying products. In order to simulate the raise of the temperature of the roofing tiles during drying the second model was used. This simple receding drying front model was firstly reported by Kitcher. If both models are used simultaneously it is possible to calculate air temperatures, product temperature, absolute and relative humidity of the drying air, moisture content of the product, drying rate etc… It is important to mention that this approach can lead to the recommendations for changes inside the dryer before an optimized situation is achieved. One example of such situations is described in this paper in details.

A novel dryer design with carbonic heating film technology and drying of high moisture lignite coal

ABSTRACT Rotary dryers are generally preferred for industrial coal drying operations. However, the initial investment and maintenance costs of rotary dryers are quite high. There is also the risk of spontaneous combustion and ignition of coal in such dryers. In this context, carbonic film technology comes to the forefront when an environmentally friendly drying system with low initial investment cost and no risk of ignition of coal. Low-temperature drying can be performed using carbonic film technology. However, there are no dryer systems drying with this technology. The aim of this study is to design a new dryer with carbonic film heater. With the carbonic dryer (CDC) designed as a result of experimental studies, the total energy to be spent for the removal of 9% moisture from 1 ton coal was found to be only 50 kWh. Furthermore, the FIR heating carbonic film is efficient for drying thin-layer coal and is inefficient at high layer thickness.

Effect of dehydration on phenolic compounds and antioxidant activity of blackcurrant (Ribes nigrum L.) pomace

SummaryThis study examined the effect of dehydration on the phenolic compounds and antioxidant activity of blackcurrant (Ribes nigrum L.) pomaces (DBP) subjected to hot air oven drying (HOD), industrial rotary drying (IRD) and freeze drying (FD). Temperature and residence time were evaluated for HOD, whereas air‐on and air‐off temperature, ratio of drum rotor speed to air speed and particle size were evaluated for IRD. The highest total anthocyanins (ATC) and flavonols (FLV) were obtained in particle size of> 5.0 mm using IRD at 475°C/97°C (air‐on/air‐off) and higher ratio of drum rotor speed to air speed. Smaller size particles were found susceptible to degradation due to high temperature and retention time applied in IRD, resulting in loss of phenolic compounds in DBP, and thus, HOD was deemed more suitable. Overall, drying method selection and parameters of operation are key in preserving the concentrations of individual HCA and FLV in DBP.

Application of Artificial Neural Network for Prediction of Key Indexes of Corn Industrial Drying by Considering the Ambient Conditions

Uncontrollable ambient conditions are the main factors limiting the self-adaption control of an industrial drying system. To achieve the goal of accurate control of the drying process, the influence of the ambient conditions on the drying behavior should be taken into consideration when modeling the drying process. Present work introduced an industrial drying system with a loading capacity of 50 t, two artificial neural network prediction models with (IANN) and without (OANN) considering the ambient conditions were established using artificial neural network modeling approach. The ambient conditions on the moisture content (MC), exergy efficiency of the heat exchanger (ηex,h) and specific recovered radiant energy (Er) of the drying process were also investigated. The results showed that the ηex,h and Er increase with the increase of ambient temperature while the drying time decrease with the increase of the ambient temperature. The IANN model has a better prediction performance that that of OANN model. An optimal architecture of 9-2-12-3 artificial neuron network model was developed and the best prediction performance of the artificial neural network (ANN) model were found at a training epoch number of 30, and a momentum coefficient of 0.4, where the coefficient of determination of moisture content, exergy efficiency of heat exchanger, and the specific recovered radiant energy, respectively are 0.998, 0.992, and 0.980, indicating that the model has an excellent prediction performance and can be used in engineering practice.

Simulation of hot air infrared‐assisted green peas drying using finite element method

AbstractThe objective of this study was to simulate the drying kinetics of green peas in a hot‐air infrared‐assisted dryer using an appropriate finite element method (FEM). To achieve the aim of the study, the axisymmetric FEM with the Galerkin approach was employed to model and predict the drying behavior. One of the key physical properties required for the modeling was to determine the effective moisture diffusivity obtained from previous study on green peas drying in a lab‐scale hot‐air infrared‐assisted dryer. To compare the simulated moisture transfer results with those of experiments several experiments consisting of combination of main factors namely drying air temperatures (30°C, 40°C, and 50°C), infrared power intensity (0 as a control, 0.2, 0.4, and 0.6 W cm−2), and drying air flow velocity (0.5, 1, and 1.5 ms−1) were conducted in three replications. The predicted average moisture contents by the proposed mathematical model showed reasonably a good agreement with the experimental data (maximum error value: RMSE = 2.18 and MARE = 5.08%). The simulation was also compared by two‐dimensional FEM. The results demonstrated that the accuracy of the axisymmetric FEM was higher than two‐dimensional FEM. Based on the results, the developed FEM model has reasonable accuracy and can be applied to provide more information on the dynamics of moisture movement without running any experiments. Furthermore, the useful information about optimum design of industrial dryers and drying behavior can be achieved by simulation of the drying process.Practical ApplicationsFood security is an important issue for every developing country. Fruits are a major source of nutrients that widely used as fresh or processed. Drying process is widely used to improve the security, quality, shelf time, and also the packaging and transportation of the foodstuff. Design of dryer requires a high degree of attention. The useful information about optimum design of dryer and drying behavior can be achieved by simulation of the drying process. In this study, the finite element method is used to model and simulate the drying process of green peas (Pisum sativum L.). Green peas are one of the ancient cultivated and nutritious popular vegetables with a most useful amount of fiber that enjoy the antioxidant and anti‐inflammatory benefits.

Optimal cascade phase change regenerator for waste heat recovery in a batch industrial dryer

Waste heat recovery is one of the main strategies to reduce the use of primary resources. This work develops a cascade phase change regenerator to recover energy from exhaust air to fresh air of a natural gas-fired batch dryer in an existing industrial laundry, taken as a case study, where an experimental campaign is conducted. The regenerator comprises two vertical stoves made of horizontal rod bundles in an aligned configuration to mitigate the fouling. The rods are hollow smooth cylinders that are grouped into sectors, each of which is filled with a phase change material properly selected among paraffins. The number of cylinders per row and the cylinder diameter are investigated by a parametric analysis; the number of sectors and the materials filling each sector are optimized by two alternative algorithms, one based on the process physics and the other on a statistical method. At last, an economic analysis is applied to the optimal configuration. This optimal configuration turns to be an 8-sector regenerator that attains an energy recovered of 61.5% and a net annual saving of 3340 €/year and that requires a total cost of about 9500 €, yielding a payback time lower than 3 years.

Two antimicrobial genes from Aegilops tauschii Cosson identified by the Bacillus subtilis expression system

Antimicrobial genes play an important role as a primary defense mechanism in all multicellular organisms. We chose Bacillus subtilis as a target pathogen indicator and transferred the Aegilops tauschii Cosson cDNA library into B. subtilis cells. Expression of the candidate antimicrobial gene can inhibit B. subtilis cell growth. Using this strategy, we screened six genes that have an internal effect on the indicator bacteria. Then, the secreted proteins were extracted and tested; two genes, AtR100 and AtR472, were found to have strong external antimicrobial activities with broad-spectrum resistance against Xanthomonas oryzae pv. oryzicola, Clavibacter fangii, and Botrytis cinerea. Additionally, thermal stability tests indicated that the antimicrobial activities of both proteins were thermostable. Furthermore, these two proteins exhibited no significant hemolytic activities. To test the feasibility of application at the industrial level, liquid fermentation and spray drying of these two proteins were conducted. Powder dilutions were shown to have significant inhibitory effects on B. cinerea. Fluorescence microscopy and flow cytometry results showed that the purified protein impaired and targeted the cell membranes. This study revealed that these two antimicrobial peptides could potentially be used for replacing antibiotics, which would provide the chance to reduce the emergence of drug resistance.

Assessment of heat pump with carbon dioxide/low-global warming potential working fluid mixture for drying process: Energy and emissions saving potential

Drying is one energy-intensive process in the industry. Heat pump system for drying process by employing carbon dioxide/low-global warming potential working fluid mixture is proposed and compared with traditional boiler drying systems. A life cycle thermodynamic and environmental evaluation model is developed to assess the energy consumption, gaseous and particulate matter emissions saving potential by using the new heat pump drying solutions. With the help of carbon dioxide/low-global warming potential working fluid mixtures, the coefficient of performance of heat pump dryer is obviously enhanced and the discharge pressure is reduced. The highest coefficient of performance of 4.29 is achieved by using carbon dioxide/R32 under the mass fraction of 0.1/0.9, which is increased by 7.42% in contrast to pure carbon dioxide. The specific moisture extraction rate is improved and the primary energy consumption throughout the lifetime is dramatically reduced. The life cycle climate performance is also reduced and the equivalent carbon dioxide emissions from energy consumption are the dominant category. Carbon dioxide-based mixture heat pump dryer can also reduce the pollutant emissions. Compared with natural gas-fired boiler system, oxynitride emissions are decreased by 81.66%, and particulate matter emissions are less than a quarter of the electric boiler. Carbon dioxide/low-global warming potential working fluid mixtures with low or medium-temperature glide, and high-temperature glide carbon dioxide/low-global warming potential working fluid mixtures with extremely low (~0.1) or very high (~0.9) carbon dioxide mass concentrations are recommended. The heat pump dryer charged with carbon dioxide/low-global warming potential working fluid mixtures is a promising solution to substitute traditional boilers for energy-saving and environmentally-friendly industrial drying.

Analysis of intermittent infrared drying using heat recovery with a novel control methodology

AbstractDrying is one of the most energy consuming process. By using automatic control systems in the industry, a higher quality and energy efficient drying is achieved. There are two main periods in drying process, the constant rate period and the falling rate period. In the falling rate period, it becomes difficult to evaporate water from the product, and this results in high specific energy consumption values and low energy efficiency values. In this study, apple slices were dried in an intermittent infrared dryer with two new developed drying methodologies as a solution to this problem (Model 2 and 3). An Arduino based automatic control system was used for Model 2 and Model 3. Developed models were compared with conventional experiments (Model 1). With Model 2, a constant drying rate was achieved independently of the moisture content. With Model 3, 57% shorter drying time compared to Model 2 and 16% less energy consumption compared to Model 1 was provided. Also using of the Model 3 the energy efficiency increased as 50% and the specific energy consumption decreased as 48% compared to Model 1. This study offers a solution with high efficiency in industrial usage.Practical ApplicationsConventional dryers have low energy efficiency and high specific energy consumption. With two novel drying methodologies developed within the scope of this study, a reduction of 16% in energy consumption and increase of 50% in energy efficiency were observed as an alternative to conventional drying. In addition, a constant drying rate was achieved independently of the moisture content. These drying methodologies offer an applicable solution for drying process with high energy efficiency in industrial food drying systems. Thus, it is foreseen to decrease the energy consumption and increase the efficiency in the drying industry, which constitutes a large part of the industrial energy consumption.

Solar‐thermal driven drying technologies for large‐scale industrial applications: State of the art, gaps, and opportunities

Research and Innovation (R&I) on Large-scale Industrial Solar-thermal driven Drying technologies (LISDs) is one of the strategies required to transition to a low-carbon energy future. The objective for this work is to guide future R&I on LISDs by defining the state of the art, gaps, and opportunities. To provide a high-level perspective on the current state of solar drying research, results are presented from an analysis of the content relevant to LISDs found in 45 solar drying Review Articles published in journals over the past 25 years. A conclusion is that most of the existing solar drying research is not focused on LISDs. To build-on these existing 45 solar drying Review Articles, results are presented from an analysis of 30 Original Research Articles with significant content relevant to LISDs published over the past 5 years. A gap is identified in coupling existing or slightly modified solar thermal collectors with existing or slightly modified industrial drying technologies to create indirect LISDs. To facilitate formulating new coupling strategies, the drying characteristics most relevant to this coupling are described and four fundamental classes of industrial dryer technologies are defined based on the underlying heat transfer mechanism, which then impacts the appropriate collector choice. At their most fundamental level, many of the technologies needed to couple solar collectors and industrial dryers to create novel indirect LISDs are not unique to indirect LISDs, but rather can be generalized across a wide range of Solar Heat for Industrial Processes (SHIP) applications, and integration issues are discussed at a more fundamental SHIP level. The technical and economic characteristics of 19 existing LISDs installations throughout the world are presented, and potential and emerging areas discussed.

Exergoeconomic Analysis of Corn Drying in a Novel Industrial Drying System.

The improvement of the design and operation of energy conversion systems is a theme of global concern. As an energy intensive operation, industrial agricultural product drying has also attracted significant attention in recent years. Taking a novel industrial corn drying system with drying capacity of 5.5 t/h as a study case, based on existing exergoeconomic and exergetic analysis methodology, the present work investigated the exergetic and economic performance of the drying system and identified its energy use deficiencies. The results showed that the average drying rate for corn drying in the system is 1.98 gwater/gdry matter h. The average exergy rate for dehydrating the moisture from the corn kernel is 345.22 kW and the exergy efficiency of the drying chamber ranges from 14.81% to 40.10%. The average cost of producing 1 GJ exergy for removing water from wet corn kernels is USD 25.971, while the average cost of removing 1 kg water is USD 0.159. These results might help to further understand the drying process from the exergoeconomic perspective and aid formulation of a scientific index for agricultural product industrial drying. Additionally, the results also indicated that, from an energy perspective, the combustion chamber should be firstly optimized, while the drying chamber should be given priority from the exergoeconomics perspective. The main results would be helpful for further optimizing the drying process from both energetic and economic perspectives and provide new thinking about agricultural product industrial drying from the perspective of exergoeconomics.

The conditioning regime in industrial drying of Scots pine sawn timber studied by X-ray computed tomography: a case-study

Industrial drying of sawn timber is a process driven by a difference in moisture content (MC) between the core and the surface as moisture moves from the wet inner region towards the drier surface. After drying, the timber surface is always drier than its core, and stresses have developed within the wood volume. If the timber is to be further processed, these stresses and the moisture gradient need to be reduced to avoid unwanted distortion, i.e. the timber needs to be conditioned. Conditioning is usually accomplished by exposing the timber to a hot and humid climate after the drying regime. The conditioning regime is essential for timber quality, and it is energy and time consuming; therefore of interest for optimisation. This research was a case study where for the first time the MC during conditioning was studied in an X-ray computed tomography (CT) scanner. The aim was to test a previously developed algorithm and investigate the influence of MC and heartwood-sapwood proportion on the effectivity of the moisture equalisation in 30 mm thick Scots pine boards. The MC was estimated from CT data acquired during the drying and conditioning of the boards in a lab-scale kiln adapted to a medical CT scanner. Results show that the algorithm can provide relevant data of internal MC distribution of sawn timber at the pixel level. Furthermore, for the drying schedules studied, the conditioning at low MC (8%) does not need to be longer than 3 h, while higher MC (18%) requires a longer conditioning.

Simulation and Analysis of Plug Flow Fluidized Bed Dryer

Today many industries now use the dryer as a part of grain-drying process even during wet and dry seasons. This helps in reducing spoilage and wastage of paddy. Mostly the available industrial dryers are expensive to purchase and to maintain its smooth functioning. This study therefore is a step to design a simple Plug flow fluidized dryer that can lead to introduce small scale dryers to paddy process industry. The Plug flow fluidized bed dryers are designed and fabricated in this study consists of the drying chamber, hot air distributer plate, hot air inlet and exit system, paddy entry and exit system, fluidization chamber unit with temperature control unit and the centrifugal fan. The evaluation of dryer is based on drying time and reduction in moisture content and outlet temperature of paddy on quality parameters. Dryer dimensions are very important to analyze heat and mass transfer analysis of the Plug flow fluidized bed drying process of paddy grains. It was found d that heat and mass transfer properties of paddy grains in fluidized bed dryer was decreases as the time of drying passes and very rapid at the start of drying. The model present here predicts about dryer dimensions along safe zone of rough rice moisture content with other parameters. Simulation results show a good agreement between the simulation model and the existing simulation models.

Design and Performance of a Parabolic trough System for Process Heat Application

The worldwide energy demand is rapidly increasing, increasing in turn the necessity of power generation. The generated power is used to fulfill domestic and industrial needs. Industries use electricity for medium scale heating applications, which is the worst use of electricity. Concentrated solar power can prove itself a superior alternative of electrical heating load, being the only technology which produces high quality heat. In this paper, a systematic design approach of a parabolic trough based solar field for a defined thermal load is presented. The performance simulation of the field has been done for a small scale, medium temperature industrial drying process of 290 kWth at 120oC, located in Bhopal using System Advisor Model (SAM), was found to be 23% efficient. The results can be used as a roadmap for designers for the feasibility analysis of local industrial application

Radio frequency vacuum drying of Eucalyptus nitens juvenile wood

Wood drying is an important process for adding value and manufacturing innovative products. Eucalyptus nitens wood is inherently difficult to dry because of its natural propensity for checking as well as collapse and shrinkage. Lumber recovery after industrial drying of eucalypts is also very low. This study measured the wood quality of E. nitens juvenile wood (13 mm thickness) after radio-frequency vacuum (RFV) drying and wood dried in a conventional kiln dryer (KD). Drying cycles were performed using a radio frequency vacuum dryer with a 3 m3 of capacity and convective kiln-dryer equipment with a 3.5 m3 of capacity. The results showed that the drying time using the radio frequency vacuum method was reduced by 47% when compared to conventional kiln drying. The shrinkage was significantly lower in the RFV than in the conventional KD. The volumetric collapse decreased by approximately 60% in the RFV drying. RFV drying of E. nitens juvenile wood improves the wood quality for solid wood products because the intensity of surface checking and collapse are reduced.

Comparison of the Effect of Traditional and Industrial Drying Methods in Raisins Production On Heavy Metals Concentrations

The present study was conducted to compare the effects of traditional and industrial methods on heavy metals concentrations in raisins. The concentration of heavy metals (cadmium, lead, nickel, copper, arsenic, and zinc) were examined in various types of raisin samples include Sultana, Golden Raisins, Shade-dried and Sun-dried raisins from Malayer city of Iran. Results showed that the mean concentrations of lead, nickel, copper, arsenic, and zinc were 0.08, 4.72, 3.07, 0.17, and 2.25 mg/kg, respectively. The concentrations of arsenic, copper, and nickel in all raisin samples were higher than the limits recommended by FAO/WHO while for zinc, and lead (80.77% of samples) was lower or in the range of the permitted values by WHO/FAO, EC, and ISIRI. Also the highest concentrations of heavy metals in raisins were observed in industrial drying methods (Sultana and Golden raisins). We identified a positive correlation between zinc and nickel in raisin samples (P < 0.01), while there was no correlation between the other elements.