Energy Consumption Of Dryers Research Articles

Design and Evaluate a Cabinet Dryer for Drying of Food and Agriculture Waste

Design and Evaluate a Cabinet Dryer for Drying of Food and Agriculture Waste

Performance of predictive control for a continuous horizontal fluidized bed dryer

Advanced process control can benefit to the operation efficiency and quality of tablets produced by wet granulation lines. Following the development of a new fully continuous fluidized bed reactor as a potential substitute for the current batch dryer design, this paper examines the energy and product quality performances of two predictive control strategies using an experimentally validated simulator. The first one proposes an economic model predictive controller explicitly minimizing the dryer energy consumption. The second one follows the same objective, but uses a simpler classical predictive control framework implementing targets on manipulated variables to drive them toward low energy consumption operating points. Both controllers lead to similar performances, and consume about 20% less energy than a reference feedback scheme without manipulated variable setpoints. Results also show that tracking the product quality attribute significantly benefits from a feedforward action because of the long residence time. This article addresses a subject little explored by the literature, the control of continuous fluidized bed dryers, and clearly demonstrates that a standard linear strategy can reduce the operating costs with an appropriate design.

Energy analysis and economic feasibility of wood dryers integrated with heat recovery unit and solar air heaters in cold and hot climates

In this paper, the energy performance and economic feasibility of conventional wood dryer systems integrated with a heat recovery unit and solar air heaters are numerically investigated. Four different designs of wood dryers, composed of an insulated drying chamber, a heat recovery unit (HRU), a flat plate air collector (FPC), a photovoltaic/thermal air collector (PVT) and an auxiliary heater, are presented and compared. Annual dynamic simulations were carried out using a heat and mass transfer model with realistic meteorological data from two different climatic zones as boundary conditions. The effect of recovering waste heat and integrating each type of solar air heaters on the wood dryer energy consumption are presented and analyzed. Results show that recovering waste heat from conventional wood dryers in cold climate is more beneficial than in hot climate with an annual energy consumption reduction up to 41%. It is also shown that using a combined heat recovery unit and PVT collector improved significantly the energy efficiency of conventional dryers and reduced by about 67.5% and 49.5% the yearly energy consumption in hot and cold climates, respectively. Based on the economic analysis, the use of the HRU is beneficial in both climatic zones with a maximum payback period of 2 years. However, the use of the PVT collector is recommended only for wood dryers in hot climates where the payback period is about 3.5 years.

THE DETERMINATION OF THE DRYING KINETICS AND ENERGY EFFICIENCY OF RED PEPPER (CAPSICUM ANNUUM L.) USING DIFFERENT DRYING METHODS AND MICROWAVE FINISH DRYING

The effects of different drying processes namely microwave (MD), freeze (FD), convective (CD), and vacuum drying (VD) and combined drying methods (FD+MD and CD+MD) on drying characteristics, effective moisture diffusivity, and activation energy of red pepper powder and total energy consumption of dryers were investigated. All drying processes took place in combined form of constant and falling rate periods for all drying experiments except for CD and CD+ MD. In order to determine drying kinetics of red pepper pulp (RPP) seven thin layer drying models were fitted to experimental data and Page (MD, FD, CD, VD, CD+MD) and Logarithmic (FD+MD) models which had the highest R2 and lowest χ2 and RMSE were found to satisfactorily describe the drying behavior of RPP. Findings indicated that compared to FD and CD alone, intermitted dried samples had significantly higher Deff (p<0.05). Specific energy consumption values ranged between 3.13 and 664.52 MJ/kg H2O

Research on an electric energy‐saving grain drying system with internal circulation of the drying medium

AbstractIn this study, we designed a 5HLN‐R‐50 electric grain dryer with internal circulation of the drying medium based on the analysis of drying medium enthalpy and humidity status variation diagrams. We aimed to reduce the dryer energy consumption and exhaust gas emission. Using clean electric energy instead of a conventional dryer heat source, the drying system can cyclically dry high‐moisture grain with zero emissions. The experimental results indicate that the condensation effect is suitable when the ratio of the cool and hot air flows is 6:1 at a heat transfer coefficient of the condenser of 79.5 W/(m2.K) and a specific heat consumption of 3,916 kJ/kgH2O when compared with the Chinese standard of 7,500 kJ/kgH2O, that is, a maximum energy savings of 48%. This paper proposes a novel technological method and idea, studies the differences in energy efficiency, emissions reduction and clean production, and provides a reference for replacing the conventional grain dryer heat source of coal with electricity.Practical applicationsThis drying system is applied in circular grain drying; a corn drying experiment indicates that compared with the specific energy consumption stipulated by the national standards of China, the highest energy savings is 48%, and zero release nonpollution is shown. The state parameters of the dried material and drying medium are displayed graphically in real time, and the operating parameters of the drying process are intuitively tracked in real time and automatically adjusted.

Investigation of rough rice drying in fixed and fluidized bed dryers utilizing dehumidified air as a drying agent

ABSTRACT* The high initial moisture content of freshly harvested rice accompanied by high relative humidity ambient air as well as no external heating source utilized for on-farm in-bin drying increase the risk of rice deterioration. Air dehumidification could be among the best management practices for rice drying in the high relative humidity environment. The current study aimed to explore the possibility of using silica gel to dehumidify the humid ambient air for drying rice in a fixed bed and fluidized bed. A dehumidification unit was added to the previously developed lab-scale fluidized bed dryer before the blower inlet to help dehumidify the moist inlet air. The effects of bed conditions, i.e., fixed or fluidized, dehumidification environment, i.e., with and without dehumidification, and air temperature; i.e., 40 °C or 60 °C on the dryer performance, were investigated. The fluidized bed dryer removed more moisture from rough rice as compared with a fixed bed dryer. Explicitly, under the conditions of a fluidized bed, no dehumidification and at 60 °C, the moisture removed was 1.5% moisture points more than under the same conditions for fixed bed. Dehumidifying the humid air removed between 0.2% and 1.6% moisture points from rough rice more than the environment of no dehumidification. Moisture content profile showed that about 87% to 90% of the moisture was removed during the first 30 minutes of the drying process. The maximum head rice yield achieved 66.7% during the drying in a fixed bed and with no dehumidification at 40 °C. However, it achieved its maximum of 64.6% during the drying in fluidized with dehumidification, and under 40 °C. The maximum rice whiteness of 41.8 was attained for fluidized with no dehumidification, and at 60 °C. The dryer energy consumption decreased with the use of air dehumidification techniques. Through this study, ambient air dehumidification using desiccant showed the noticeable potential to be used for on-farm in-bin ambient air drying, particularly during humid conditions. Highlights A fluidized bed drying system was modified to allow utilizing natural or dehumidified air as drying agents. The fluidized bed dryer removed more moisture from rough rice as compared with a fixed bed dryer. Dehumidification of the drying air had a positive effect on moisture removal. No clear trend was observed when rough rice was dried in a fixed bed or a fluidized bed as measured by head rice yield.

Optimization of energy consumption of a solar-electric dryer during hot air drying of tomato slices

High-energy demand of convective crop dryers has prompted study on optimization of dryer energy consumption for optimal and cost effective drying operation. This paper presents response surface optimization of energy consumption of a solar-electric dryer during hot air drying of tomato slices. Drying experiments were conducted with 1kg batch of tomato samples using a 33Central Composite Design (CCD) of Design Expert 7.0 Statistical Package. Three levels of air velocity (1.0, 1.5 and 2.0ms–1), slice thickness (10, 15 and 20mm) and air temperature (50, 60 and 70oC) were used to investigate their effects on energy consumption. A quadratic model was obtained with a high coefficient of determination (R2) of 0.9825. The model was validated using the statistical analysis of the experimental parameters and normal probability plot of the energy consumption residuals. Results obtained indicate that the process parameters had significant quadratic effects (p < 0.05) on the energy consumption. The energy consumption varied between 5.42kWh and 99.78kWh; whereas the specific energy consumption varied between 5.53kWhkg–1and 150.61kWhkg–1. The desirability index method was applied in predicting the ideal energy consumption and drying conditions for tomato slices in a solar-electric dryer. At optimum drying conditions of 1.94ms–1air velocity, 10.36mm slice thickness and 68.4oC drying air temperature, the corresponding energy consumption was 5.68kWh for maximum desirability index of 0.989. Thermal utilization efficiency (TUE) of the sliced tomato samples ranged between 15 ≤ TUE ≤ 58%. The maximum TUE value was obtained at 70oC air temperature, 1.0ms–1air velocity and 10mm slice thickness treatment combination, whereas the minimum TUE was obtained at 50oC air temperature, 2.0ms–1air velocity and 20mm slice thickness. Recommendation and prospect for further improvement of the dryer system were stated.

Optimisation of energy consumption of a solar-electric dryer during hot air drying of tomato slices

High-energy demand of convective crop dryers has prompted study on optimisation of dryer energy consumption for optimal and cost effective drying operation. This paper presents response surface optimisation of energy consumption of a solar-electric dryer during hot air drying of tomato slices. Drying experiments were conducted with 1 kg batch of tomato samples using a 33 central composite design of Design Expert 7.0 Statistical Package. Three levels of air velocity (1.0, 1.5 and 2.0 ms–1), slice thickness (10, 15 and 20 mm) and air temperature (50, 60 and 70°C) were used to investigate their effects on energy consumption. A quadratic model was obtained with a high coefficient of determination (R2) of 0.9825. The model was validated using the statistical analysis of the experimental parameters and normal probability plot of the energy consumption residuals. Results obtained indicate that the process parameters had significant quadratic effects (P<0.05) on the energy consumption. The energy consumption varied between 5.42 kWh and 99.78 kWh; whereas the specific energy consumption varied between 5.53 kWhkg–1 and 150.61 kWhkg–1. The desirability index method was applied in predicting the ideal energy consumption and drying conditions for tomato slices in a solar-electric dryer. At optimum drying conditions of 1.94 ms–1 air velocity, 10.36 mm slice thickness and 68.4°C drying air temperature, the corresponding energy consumption was 5.6 8kWh for maximum desirability index of 0.989. Thermal utilisation efficiency (TUE) of the sliced tomato samples ranged between 15 ≤TUE ≤58%. The maximum TUE value was obtained at 70°C air temperature, 1.0 ms–1 air velocity and 10 mm slice thickness treatment combination, whereas the minimum TUE was obtained at 50°C air temperature, 2.0 ms–1 air velocity and 20 mm slice thickness. Recommendation and prospect for further improvement of the dryer system were stated.

Modeling of heat pump tumble dryer energy consumption and drying time

The use of heat pump tumble dryers is nowadays more common because they offer huge energy savings compared to conventional tumble dryers. Earlier studies made on conventional tumble dryers have shown that parameters such as heater power, fan speed, drum speed, weight and initial moisture content of textiles and air leakage have a huge impact on the energy efficiency and drying time. In the present study, a modified commercial heat pump tumble dryer was evaluated for energy consumption and drying time by changing operating parameters including fan speed, drum speed, and mass load. The total energy consumption and drying time were measured and corrected for the initial and final moisture content in the textiles. The experimental results based on 27 drying tests were evaluated to develop linear regression models for energy consumption and drying time, which show a good agreement with the experimental data. The results show that a large mass load, a high drum speed, and a low fan speed give the highest energy efficiency, i.e. the lowest energy consumption per kg of drying load. Larger loads extend the length of the drying cycle while higher fan and drum speeds result in shorter drying time.

Impact of ammonia fiber expansion (AFEX) pretreatment on energy consumption during drying, grinding, and pelletization of corn stover

ABSTRACTPretreatment and densification of biomass can increase the viability of bioenergy production by providing a feedstock that is readily hydrolyzed and able to be transported over greater distances. Ammonia fiber expansion (AFEX™) is one such method targeted for use at distributed depots to create a value-added and densified feedstock for bioenergy use. However, the pretreatment process results in a high-moisture material that must be dried, further size reduced, and pelletized, all of which are energy-intensive processes. This work quantifies the energy consumption required to dry, grind, and densify AFEX-pretreated corn stover compared to non-pretreated stover and explores the potential of reduced drying as a means to conserve energy. The purpose of this work is to understand whether material property changes resulting from AFEX pretreatment influence the material performance in downstream formatting operations. Material properties, heat balance equations, and a rotary drum dryer model were used to model a commercial-scale rotary drum dryer for AFEX-pretreated corn stover, showing the potential to reduce dryer energy consumption by up to 36% compared to non-pretreated corn stover. Laboratory-measured grinding and pelleting energies were both very sensitive to material moisture content. Overall, the total energy required for drying, grinding, and pelleting amounts to a savings of up to 23 kWh/dry Mg for the AFEX-pretreated material when dried to a low moisture content, equating to up to 0.61 $/Mg savings for gas and electricity. Grinding and pelleting of high-moisture AFEX-pretreated stover was shown to be more costlier than the savings collected through reduced drying. Although the energy and cost savings shown here are modest, the results help to highlight operational challenges and opportunities for continued improvement.

Energy Intensity Diagnostics Contributed to Solar Dryers Energy Challenges

The energy consumption of dryers as an energy-intensive industry system is discussed in the present paper. In order to reduce this energy amount, solar dryers were applied since ancient times, among these kinds of dryers, high drying rate solar dryers include fluidized bed and spouted bed were discussed in this research study. The experiment and calculation results depicted that, the fluidized bed solar dryer has higher drying rate than spouted bed dryer, even though, spouted bed dryer has less energy intensity consumption.

Development of design charts for tunnel dryers

A dryer simulation model, comprising a material model and an equipment model, has been developed for the drying of food products in a tunnel dryer. The material model, which deals with the drying kinetics of the product, is based on the receding evaporation front phenomenon while the equipment model describes the dynamics of the dryer. The overall model takes into account the shrinkage of the product. Simulation results of the transient moisture content show good agreement with experimental results for two dryers of different drying capacity. We present a design chart relating air temperature and humidity to the required energy for drying and dryer length, which shows an appreciable effect of setting low humidity for low temperature drying. A reduction in dryer energy consumption and chamber size is obtained under this condition. Multi-stage drying is introduced for situations where saturation of the air is likely to occur in the drying chamber. © 1997 by John Wiley & Sons, Ltd.

Development of design charts for tunnel dryers

A dryer simulation model, comprising a material model and an equipment model, has been developed for the drying of food products in a tunnel dryer. The material model, which deals with the drying kinetics of the product, is based on the receding evaporation front phenomenon while the equipment model describes the dynamics of the dryer. The overall model takes into account the shrinkage of the product. Simulation results of the transient moisture content show good agreement with experimental results for two dryers of different drying capacity. We present a design chart relating air temperature and humidity to the required energy for drying and dryer length, which shows an appreciable effect of setting low humidity for low temperature drying. A reduction in dryer energy consumption and chamber size is obtained under this condition. Multi-stage drying is introduced for situations where saturation of the air is likely to occur in the drying chamber. © 1997 by John Wiley & Sons, Ltd.